Airspy ADC1 HF - without HF upconverter

About a month ago I bought a used Airspy and have been using it with good results since then.  Anyone who's been following this blog knows I've been in search of the most frequency stable SDR setup I could build or cobble together for several years.  I think I've finally come up with a combination that meets my requirements.

I am an avid CW operator on the Ham bands.  So any drift from an RTL, Funcube, HackRF, Airspy setup makes it a hassle to continually re-calibrate HDSDR for the drift-of-the-moment.  Some setups (even the Nooelec TCXO RTL) drift way to much to be useful and practical for CW operation.

My setup is like this.  My Primary Transceiver is a Yaesu FTDX-5000.  It comes with a 9 MHz IF output on the back of the radio.  This is then connected to whatever I'm using as the SDR to feed HDSDR software with IQ data in order to visualize the band I'm on.

Since 9 MHz is lower than most of the Cheap SDR's can tune to (most seem to stop around 24 MHz for the low end) I've needed to use an HF Upconverter.  The commonly available upconverters have drift of their own which further exacerbates the overall displayed drift.  Total drift on some setups has been as much as 1khz!  So when I'm using narrow filters, and trying to click-tune to a signal I see I end up way off the actual signal, and have to fiddle around to try to get zero-beat on it.  

I spend most of my time on 50 MHz, so this 'fiddle-time' can mean the difference between coping a callsign, and never hearing it again.

After reading reviews and doing a little research on the Airspy SDR I decided to buy one.  Two major factors for me that seemed encouraging are that the Airpsy is a 12 bit SDR instead of only 8 bit.  This a huge difference.  The other was that the Airspy has the ability to be 'clocked' by an external 10 MHz source.  It so happens that I have a Jackson Labs "Fury" GPSDO which uses GPS to generate an accurate 10 Mhz Sinewave as a clock output.  This is then connected via an SMA<>MCX connector and plugged into the Airspy.  The Airspy detects that the signal exists and syncs it's internal clocking to it which causes it to never really deviate (drift) in frequency.  I have yet to see it drift using this setup.  

The trouble that still existed was that I still needed to use an upconverter to get my 9MHz IF into a range that the Airspy would receive.

I recently read that it was possible to connect an HF antenna to the "ADC1" port internally on the Airspy.  I read that there was also some special Firmware developed to enable use of the ADC1 as the Airspy's input.  So I bought a cable with the proper connector to fit the port on the Airspy, I connect that to an band pass filter, and the filter connects to an LNA which then connects to the 9 MHz IF out from the FTDX-5000.  I flashed the firmware on the Airspy with the special firmware to enable use of the ADC1, and talked IW0HDV into creating a special EXTIO DLL that would UNLOCK the low end (HF<24 MHz).  He sent me an experimental version this past weekend and today I set this all up as I just mentioned.

And wah-lah!  It all works.

Note the small coax and connector at the bottom of this picture.  This is the connector and coax that runs from the ADC1.  The MCX/SMA on the right side is the GPSDO input connector.  The white cable is the USB for the Airspy.  NOTE: that the normal SMA connector is not used.

Bottom of the image shows the Mini-circuits BPF (band pass filter) above that is the LNA HF http://lna4hf.blogspot.com/ top of the image runs directly to the 9 MHz IF from the FTDX-5000.

Stay tuned for some more images, and possibly some video of HDSDR running with this configuration.

Update

After a few weeks of testing a few very strong openings on 50 Mhz (40/s9 type openings) I realized that I needed to be able to control the signal strength input to the Airspy.  I tried to simply add a 30 db step attenuator inline, but as soon as I added as little as 1db all signals would drop out on HDSDR.  

I contacted W9RAN who was the first I'd seen attempting to use the DDC method to operate the Airspy on HF.  After some discussion I decided what I need to try to do was to increase the gain, and see if I could use the step attenutor without signals completely dropping out.

I added a 34dB+ gain Miteq LNA which covers 1-100 MHz.  And a static 10dB minicircuits attenuator.  This sould give me about 24db gain to play with.  And I can then attenutate signals to -6dB below what is coming out of the FTDX-5000.  The point being I need to be able to see weak EME type signals but be able to attenuate way down when need be.

This seems to work.  I can operate the 30 dB step attenuator all the way through Max from 0 without having HDSDR completely drop out.

I have a second 30 step attenuator I may attempt to add to the chain for those extremely strong 50 MHz openings.

On HF I have a lot of local line noise garbage, but this'll give you an idea how it works at least.  I mostly work 50 MHz here.  Also I don't use the Audio output form HDSDR except to feed IQ to CW Skimmer.  So I don't normally use the audio out to 'listen' to.  It just gets piped to VAC and on to CW Skimmer.

I'm also seeing some images in this that are probably coming from up-band, so I'll be working on a better pass band filter for this.

Also this demo doesn't really show you what I was most concerned with unfortunately; that being freq drift of the TCXO RTL vs. Airspy.  But I'll just note here that the drift is ZERO.  Nothing I can detect anyway.  It works perfectly for my needs.

HackRF One - EXTIO DLL - HDSDR (WORKS!)

I've been searching for an EXTIO DLL for the HackRF One that will work with HDSDR for years now.

https://github.com/jocover/ExtIO_HackRF

Finally came across this today!  AND BONUS!  IT WORKS!

I contacted the author and asked him to add some smaller sample rates of 4 and 2 MSPS.  He did that and posted the new release in just about 1-2 hours.  This is useful for weak-signal stuff I most do.  It allows the ability to get HDSDR's "Resolution Bandwidth" down to 7.6 hz when MSPS is @ 2.  Which in my experience shows weak CW signals up very well!

A little about how I use HDSDR. 

I use the 9 MHz IF OUTPUT from my Yaesu FTDX-5000 as the input source to whatever SDR I'm using to feed HDSDR.   I've been using a TCXO based Nooelec RTL and an OCXO upconverter I built myself.  Even with all that 'stability' the TCXO RTL drifts all the time.  Which is a total pain in the butt for CW over the coarse of a day.

After swapping out the EXTIO for RTL in my HDSDR install I fired it up with HackRF.   Although the HackRF has advertised a low range of 30 MHz or my experience has been that it works just fine down as far as 3.5 MHz in it's stock config.  Mine is about 1.5 years old now with recent firmware installed.

Anyway I setup HDSDR initially to use 9,000,000 hz.  HDSDR has a nifty option to display the VFO frequency of the Yaesu FTDX-5000 as it's frequency regardless of what input you're really using (9 MHz in my case).

There is also a way to automatically remove the DC Spike that would show up in the middle of the display if left as noted above.  To accomplish this I set the OPTIONS > RF Front-end Frequency "IF frequency" to 9098000 and the Global Offset to 98067.  This pushes the DC Spike well below my normal viewing area, and then the 'Auto RX DC Removal' notches it down to nothing.

In this way the DC spike goes away but everything stays lined up PERFECTLY for CW.

I also connected a GPSDO I've had around for a long time that I use with my Apache Labs "Hermes" SDR.  Tee GPSDO emits a super stable 10 MHz signal that Hermes and now the HackRF lock onto.  

In a 24 hour test just completed there was 0 hz drift noted on the HackRF.  Which is what I had expected (and hoped for).  This has been my experience with the GPSDO and Hermes so I didn't expect any difference.

------------

So all of this Eliminates use of an RTL (which are drifty little bastards, but VERY VERY useful I've used them for over 5 years now with very good success), and because the RTL's are limited to 24 MHz I have always used an Upconverter which has the potential to add noise from it's OSC, and add drift to the resulting signal input to the RTL.

I'm using the HackRF because it's what I have currently and because this EXTIO is now FINALLY available.

I plan to also buy and test the AirSpy and SDRPlay at some point since I've read they hear better than the HackRF.  BUT at this point I think I can actually relax after years of muxing around with RTL's that drift like crazy and spending way to much to make a $8 device do something it doesn't really wanna do LOL.

Time will tell, but for now I'm setting my upconverters and RTL's to the side to collect some MUCH NEEDED DUST.

Double Conversion Frequency Upconverter

The 100 MHz upconverter I've built seems to work VERY well.  I don't have any complaints as it is right now.

For the sake of experimenting, and trying to learn I've decided to try to increase the distance between the LO and the Pass Band.

In the 100 MHz upconverter there's only 9 MHz between the LO and the final pass band.  I want to try to increase that distance to have as much reduction of the LO in the final pass band as possible.  (I don't think this is required to be honest, which is why I already mentioned this is for the sake of experimenting).

I enjoy working with RF Filters so I thought this would be a chance to build two of my own (and spend some more money on an already completed project LOL).

So the idea I'm going to try looks something like this block diagram below including the filter designs to reduce the LO(s) as much as possible.

This is all subject to change, but I just wanted to post the idea I'm playing around with at this point.  I will also have available a MK-3 by mini-circuits which is a frequency (doubler) Multiplier.  I may play around with that, and then rework the filters again.  But that's just something I was kicking around with.  I could (I think) use it at the 19 MHz Mixer on the 10 MHz LO and end up with 29 MHz out of that mixer (I think), which would make it even easier to build the second LO BPF since there would then be 29 MHz from the 100 MHz second LO and the final pass band.  That's just something I've been toying with in the back of my mind.  Again I don't really thing any of this is needed at this point.  My 100 MHz upconverter is working great (so far) even in the face of some very strong signals.  I just want to learn more is the bottom line.  

Parts for this modification have already been ordered.  So this is the next revision based on my 100 MHz up-converter noted previous on this blog.

Building and Characterizing RF filters with simple and cheap tools

(UPDATED 2015-03-06)

SEE ALSO: 100 MHz upconverter, and Double Conversion upconverter

I have a need to build a steep skirted RF High Pass Filter.  The filter I'm going to try to build isn't maybe the best/perfect option, but I'm looking at it more as a test and learning experience.  So I can't claim thiis to be the perfect option.  

With that in mind, and wanting to do this as cheaply as possible here are some of the details about this little mini-project.  The FTDX-5000 has a fixed 9 MHz IF output.  It's pretty difficult to obtain or build a HP filter with a sharp enough skirt where we don't have a high insertion loss, or not enough reduction in gain in the unwanted Lower portion of the filter when I'm  using a 9 MHz input to the single-stage upconverter.

In order to attempt push the boundaries a bit, I'm thinking I will try to use a frequency doubler/multiplier on the 9 MHz IF OUTPUT from the FTDX-5000.  This will give me 18 MHz separation between the LO and the Pass Band, instead of only 9 MHz.

This comes at a cost of -11db on the resulting 18 MHz signal from the original 9 MHz.

•  9MHz x2 = 18 MHz using MK-3 http://www.minicircuits.com/pdfs/MK-3.pdf $60.00 shipped. I don't think this will work!  I'm pretty sure this requires a very high input level that the 9 MHz IF won't have.  
• It's probably better to think about doing a double up-conversion using a second OCXO like a 12.8 MHz = 9 MHz = 21.8 MHz instead!  These 12.8 MHz OCXO's are 2x the cost of the 100 MHz OCXO I already have.  But building the filters is much simpler since we have a larger band spread and things become a lot easier from a filter sharpness perspective.  
• The down side is that if we're not really careful with the filters we end up using we could actually be introducing MORE spurs, noise etc...

This also means I'll have to swap out the HF Band Pass filter I've *been using* (a Minicircuits ZX75-12+) - Probably another mini-project filter to do there too I guess.  By the time this whole thing is done I'll probably had to build all of my own filters instead of getting off the shelf stuff.  The only issue with doing that is that manufacturers and re-sellers these days are really pushing SMD/SMT parts.  The last batch of parts I got were no larger than a spec of pepper.  Literally, and I had to abandon that one and reorder larger inductor coils and ceramic disc caps.

The filter I'm wanting to build is intended to reduce the 100 MHz OCXO oscillator main carrier by 55-60 db below the 118 MHz+ Pass Band I want to make use of.  Since I don't need this 100 MHz carrier in the pass band that flows into the Nooelec 0.5ppm RTL SDR Dongle I'm trying to eliminate it from being passed into the Dongle as much as possible.  The idea being that I just don't want it to de-sense the receiver in the RTL Dongle.

Honestly I'll be pleasantly surprised if this has a noticeable positive impact on the 118 MHz+ Pass band desired.

The filter I've come up with reduces <= 104 MHz by at least -65db to -69db while only reducing 118 MHz+ by about -5.53db effectively 'insertion loss' at my desired frequency.  So the net effect should be (-65 - -5.53) = -59.47db.  That seems like a pretty good reduction of the LO showing up in the input to the RTL Dongle.  Currently it's about +5db above the 109 MHz+ desired pass band where I'm not using a frequency doubler.

The new HP filter I'm planning to build will have a -5.53db insertion loss at 118 MHz.  That's
the 100 MHz LO + the 18 MHz (9 MHz X2).  For a total loss of -16.63db.  I'm not too concerned about this at this point as I have an +22db LNA available for HF (LNA4HF).

(using Iowa Hills RF Filter Designer v2.2)

So what I'm hoping this might accomplish for the upconvertion process is to reduce spur images showing up in the Pass Band.  (not that there are many at all, in fact at this point I can't really see much of that going on)  So this is just a sort of research/test and development/learning process for me.  I have an idea, and I want to test if it helps or not, or doesn't do anything all, or makes things worse.

I've already added a 41db voltage variable attenuator.  So there should be plenty of options for optimizing the RX chain.

I'll post everything about this as begin this mini-project on THIS page.  I've already ordered the parts and I'll post the parts list here asap with design details on the filter etc.

This is a work in progress updates will be coming as I get them.

KEY POINTS

• Iron Hills Filter Designer (Freeware) & Notes [Download]
• Touchstone RF Analyzer (Free Version) [Download]
• Nooelec Ham-It-Up v1.2 w/Noise Source option installed [Buy Ham-it-up] & [Buy Noise Source Kit]
• Filter Parts List
• All Parts Numbers are from http://www.mouser.com except those notes as http://www.digikey.com
• ----------------------------------------------------------
• SMA EDGE MOUNT JACK (Female): 538-73251-1150 (INPUT)
• SMA EDGE MOUNT (Male) 712-CONSMA013.062 (OUTPUT)
• ----------------------------------------------------------
• Ceramic Disc Capacitors 5%
• 24 pf   $1.01 x1
• 120 pf  $0.90 x1
• 20 pf  $0.71 x2
• 33 pf  $0.19 x3
• 15 pf  $0.34 x1
• 27 pf  $0.31 x1
• Coil craft
• 1812SMS-56NJLB Air core RF inductor 56 nH
• 1812SMS-R12JLB Air core RF inductor 120 nH
• 1812SMS-R15JLB Air core RF inductor 150 nH
• 1812SMS-82NJLB Air core RF inductor 82 nH
• 
  
• Construction Photos & Notes
• Test Results (Touchstone RF Analyzer, and resulting spectrum differences at the RTL Dongle)

Related Testing (NW0W)

TEST SETUP WITHOUT LNA(s) - Using "HAM IT UP" Noise Source

SBP21.4+ (on the HF input from NS)

ZX75HP-44-S+ and Par Electronics VHF-FM Notch Filter on the output

TEST SETUP WITHOUT LNA(s) - Using "HAM IT UP" Noise Source

SBP21.4+ (on the HF input from NS)

ZX75HP-44-S+ and Strosberg Eng. FTL201A FM-Bcast Notch Filter on the output

Related Results using Touchstone RF Analyzer + RTL 

W2AEW use of the Ham-It-Up Noise Source

Inspired by (Adam Alicajic ~ 9A4QV)

Touchstone RF Spectrum Analyzer Software

(ALSO SEE)

I wanted to have a quick and simple view of a large bandwidth that's being sent into my RTL Dongle.  Basically I wanted to SEE how altering the various low pass, and high pass, and band pass filters in my 100 Mhz Upconverter affected the output being sent to the RTL Dongle.  I came across this video showing how Touchtone's "RF Spectrum Analyzer Software" (I used the FREE version) could be used with one of these dongles to get a sense of how a filter is functioning.

(this is NOT MY Video, but demonstrates what I wanted to do basically)

Seems to work well enough!  I can now see what I wanted to be able visualize.

This was BEFORE I added a FM Broadcast band NOTCH filter AFTER the Upconverter

and just in front of the RTL Dongle.  NOTE the spectrum shape just above 105 Mhz is similar to the Band Pass filter shape I have at the input to My Upconverter.  LO Freq of 100 Mhz is at -65 dbm

This was AFTER I added a FM Broadcast band NOTCH filter AFTER the Upconverter and just in front of the RTL Dongle.  Notice the dramatic different in spurs around the 100.0 Mhz LO frequency and also the LO is down around -89dbm  Also the very different shape of the pass band around 109-115 Mhz.

While this example didn't show me what I'd hoped for, it DID show me reality of how this filter affected the results.  SO the lesson learned here is that this is a FREE and USEFUL Tool if you are attempting to visualize the effects of filtering.

I think what I'm actually looking for is a NOTCH filter that stop hard around 102 Mhz, however, this sort of thing can be quite difficult to find.  I'm basically trying to minimize the LO as much as possible or at least get it to be lower than the pass band from 109-115 Mhz. 

Anyway, I just wanted to share this with folks in case anyone else is trying to visualize the effects of a filter.  Of course, the thing to do REALLY is to inject a wide band noise source into the filter, and measure the output using software like this.  By the way, the "Ham It Up" upconverter has a noise source built in (minus a few simple addon parts to activate it.  It's a cheap way to get a decent noise source however.

HF Upconverter - Assembly and Initial Testing

SUCCESS!

After a few days or working on my new HF Upconverter I got it working!  I'd been waiting for some Buck type DC-DC converters.  So I could connect the OCXO (3.3vdc) up to the 13.8vdc from my primary Astron RS-35M.  One of the Buck converters drops 13.8vdc to 12.0 vdc, then a second one drops it again from 12vdc to 3.3vdc.  They seem to be working fine.  The 12vdc is variable.  The 3.3vdc is not which is kind of a bummer, but it's at idle on my Fluke meter 3.29vdc. (probably close enough although if I'm going to the trouble of an OCXO I'd like the PS's to be adjustable).  I'll probably hunt around for a Buck DC-DC 12-3.3vdc that is adjustable.  These things are CHEAP on ebay.  Total spent on both was around $15.00 combined including shipping.  Which beats spending hours building them at this point.

I am running the OCXO HF upconverter right now as I type this, and it seems to be rock solid so far.  No FM Bcast interference (which I didn't think I'd have with all the shielding).

I have a fair amount of work to do yet on this.  However, the fact that the SBL-1+ Mixer and the OCXO work as expected is definitely encouraging.

I am listening right now to 14 Mhz Morse Code on the FTDX-5000 and also on SDR# at 109 Mhz.  (remember the FTDX-5000 uses a 9Mhz IF Output that I'm tapped into, so the actual VFO frequency is irrelevant since all signals are sent out in the 9 Mhz realm.

Anyway...I just wanted to post that as simple as this is right now and working as well as it is, I can't wait to add the Lo and Hi pass filters to my Homebrew HF Upconverter that is accurate to within 200ppb (that's parts per BILLION)!  NO DRIFTING has been noted in my testing thus far.

Tomorrow I'll start it up from cold, and see if there is any noticeable.  I'll also post some updated pictures of where the project is now.

Things are subject to change until I setting on a mixer.  While the SBL-1+ works fine I'm curious how well the the other two I ordered from Minicircuits will work.  The are supposed to be better, and certainly should be at 4-7x the cost of the SBL-1+ (which was only $9.95).

This is FUN STUFF!

100 Mhz OCXO 200ppb For Home Brew Upconverter

I still have some work to do on this.  The closest (bottom left) (pin 1) large pad get +1.15-2.15vdc via resistor network voltage divider that bridges over from the large pad behind it  (pin 14) that is the +3.3vdc Power Supply pin.

The SMA is the 100Mhz @ 200ppb output from the OCXO which comes off pin 8.

The resistor network I was talking about is a voltage divider in the standard configuration of R1 and R2 except that I've slightly modified it to include a 1-turn 1000 Ohm Potentiometer which should allow fine tuning the OCXO by as much as -500hz and +500hz.  Hopefully this won't be needed much as that the point of having the OCXO to start with, but it simplifies retouching tuning quite a bit and seemed simple enough to add (as long as my design holds up!).

There will be a KNOB on the front of this which allows easy access for tuning the OCXO to mate up with the signals on the 9 Mhz output of the FTDX-5000.  INSTEAD OF having to go into HDSDR software's option menu and extio menu to adjust things (WHICH DRIVES ME NUTS!).

I hadn't realized that I had to provide a Vcc for pin 1 initially, and at first when I discovered this I didn't really like the idea.  Still not sure I do frankly, BUT since it adds a feature I hadn't thought of to start with I figured why not make it something I can make use of, instead of simply setting pin 1's voltage to 1.65vdc which SHOULD place the OCXO at 0pmm/0hz offset from 100 Mhz.

This "feature" provides a much as 1 full Khz adjustment (I think, according to the doc's I've read).

HF Upconverter - Home Brew (sort of)

(smoke testing components)

(Partially built, still working on final placement)

The TOP SHP-100A+ which is a HP Filter feeding the RTL Dongle is going to get replaced with a High Pass Filter I'm going to build.  My own filter will be VERY sharp and drop the 100 Mhz Carrier from the Oscillator down about 53db from where it is now, while leaving 107+ Mhz open.  My Filter will have about 5db insertion loss at 109 Mhz, but I'm also planning to add a LNA after the filter which will allow me to overcome that loss somewhat.

The Empty space top LEFT will contain a +20vdc DC-DC boost converter as well as a LM117 voltage variable regulator +17vdc to 1.2vdc to power a 41db voltage variable Attenuator and a pot will be added with a second knob to control it.

I'm also planning to add a PTT actuated RF Relay to switch out the RF input when my primary radio (and FTDX-5000 transmits) as I don't like the output of my Transmit via the 9Mhz IF output showing up in my Pan Adapter output.

The only dismal be at this point is that the Nooelec 0.5ppm RTL Dongle doesn't really seem to be living up to what I'd expected.  From a cold start it takes 15-30 minutes to (mostly) stop drifting.  But I suppose that's what you get with a TCXO (I don't really know).  I do know at cold start up it drifts in excess of 700 Khz, before it's really starts to settle down.

This is NOT the fault of the FTDX-5000 or the featured 100 Mhz upconverter I've built.  The upconverter after about 45 seconds basically doesn't drift.  It's pretty amazing and well worth the $74.00 I paid for it (for my needs, it's worth it anyway).

-------------------------------------------------------------------------------------------

I've started to work on building my own HF upconverter that will use an OCXO that is stable to 200ppb (that's 200 parts per BILLION!), not something typical like the 25ppm, 5ppm's that are commonly available for a very reasonable cost.

(click to see larger)

The idea here is that I am primarily a CW operator.  My current Pan Adapter setup runs off the 9 Mhz IF output from my Yaesu FTDX-5000.  This then routes through a LNA, Bandpass Filter, and into an HF Upconverter where it comes out at 134 Mhz...this is where the RTL SDR Dongle operates via HDSDR.

I had a RTL SDR Dongle which was stable to about 60ppm, and the HF Upconverter was stable to about 25ppm for many years.  This meant that there was almost always some dicking around involved with keeping the Pan Adapter Software "HDSDR" lined up with the FTDX-5000's stable IF output.  Thing could drift at least for several hours slowly up the band until it warmed up and as long as the Temperatures in the room didn't vary too much things were 'close enough' to be useful.

NOW I have a 0.5ppm RTL SDR Dongle.  This thing is quite accurate, however my old HF Upconverter was still only accurate to 25ppm.  So I swapped out it's 125 Mhz LO with a TCXO that was stable to 5ppm (more or less, mostly LESS) the net result was that after about 2.5 hours the total drift was around 1.1Khz.  This is still REALLY CRAPPY for CW (Morse Code) which is very narrow bandwidth.

While Talking to Nooelec.com recently we swapped emails back and forth for quite some time.  I found better TCXO's, and then came across the idea of using an OCXO.

The benefit of an OCXO is that they warm up VERY quickly compared to other LO's and once warmed up remain VERY stable.  Trouble is I could only find an OCXO that is in the 100 Mhz LO range which could get me to the 200ppB level at a reasonable price and delivery time.  So that's what I'm going with for this little mini project.  The downside to using a 100 Mhz LO is that the output of the 9 Mhz IF from the FTDX-5000 will be one 109 Mhz.  Pretty close to the FM Broadcast band.  In the past I've not had a lot of trouble with this sort of thing, mostly because I used a FM Broadcast Band STOP Filter in line with everything.  

So I can't really use the Band STOP Filter anymore.  However, this may not really be a problem.  The LNA4HF has a LO Pass filter, which should keep anything > 30 Mhz out of the primary input.  So that will help.  I'll keep all the coax lines very short (just a few inches) and use female-female type connectors to link all the components together.  I'll also keep everything shielded, and grounded as best I can.  I think this will work out ok.  

I'm planning to use an LNA4HF which includes a LOW-PASS filter in it already.  This then will route to a Mini-Circuits SBL-1+ Mixer.  Also I'll be using a 100 Mhz LO (200ppb) going into the SBL-1+ Mixer.  Output of that will route into the RTL SDR Dongle from Nooelec.

This "SHOULD" result in a MUCH more stable upconverted signal being fed into the RTL SDR Dongle.  That's the plan at this point anyway...this is sort of a side-project, but I wanted to share my thoughts on attempting to do this.

This is a review of a similar device and should help if you don't quite understand the problem I've been describing. 

I'll post more details on the various bit's and pieces I use and pix of the finished project when I'm done.

Also a Note: Nooelec.com says they're working on something new that may resolve all of this within 10-12 weeks, and something else in the range of 3-6 months.  They wouldn't indicate what exactly they were talking about.  So that's why I'm moving forward with this little end-of-winter mini-project.

More details and where to get the various components I use as I get them.  Most of this I already know, but some may change.  So...stay tuned. (no pun intended! HAR!)

Here is a list of what I'm planning to use and where I got them:

• Nooelec 0.5ppm RTL SDR Dongle
• 100 Mhz OCXO (200ppb) (3.3vdc) [datasheet] - [MORE DETAIL ON THE BUILD]
• LNA4HF (12vdc)
• 13.8 to 12vdc Buck Converter (test may not use this)
• 3.3vdc Buck Converter (to power the OCXO from a 12vdc supply)
• Mini-Circuits "SBL-1+" Mixer

Here is an example of how simple this really is:

VIDEO (Adam Alicajic)

VIDEO (W2AEW)

While this is super simple to setup as seen in his video, I expect that I'll have some technical issues getting this to work as well as my "Ham It Up v1.2", at first.  But that's OK, because it should be way more stable than the Ham It Up since it's using an OCXO.  (I sure hope).

Anyway, this is going to be a learning experience for me.  I've never done this before, at least not like this.  I'll post mod's to this plan right here on this page as updates.  

One thing I'd like to do is in front of the LNA4HF would be to place a 9 Mhz Band Pass Filter that is 2.5 Mhz wide.  I don't really know how wide the 9Mhz IF is coming out of the FTDX-5000 but it seems to be at least THAT wide.  THE LNA4HF's LO Pass Filter should keep a lot of crap out of things to start with.  This idea is just to have more control of what gets in is all.

I MAY have to attenuate the OCXO output a bit, I've heard these things can be really strong, and if so I may have to use some in line attenators at least I may have to experiment around with that some.

I added some more filters after reading THIS and THIS to my design.

WARNING: my resulting design is meant to be modular enough to I can play around with OFF THE SHELF things as I wish.  This isn't a FROM SCRAP project and therefore it's a LOT more pricey than it would really need to be.  So be advised I'm already aware that I'm going at this from an expensive direction, and that there are cheaper ways to get/build filters etc.  This is intentional for what I'm attempting to do.  

NOTE ALSO: I'm aware that it's possible to get and use OTHER LO frequencies for this upconverter and that using a 100 Mhz LO can be problematic.  (so you don't have remind me :-)

Mixers I will test with:

The SBL-1+ from MiniCircuits looks like THIS.

The ZX05-1L+ from MiniCircuits looks like THIS.  (but costs 2/3 more @ around $37.00) It's advantages include already mounted SMA connectors all around.  Specs aren't the same as the SBL-1+ but they are similar enough that I may try one of these in the future. UPDATE I actually have ordered this, and one other similar.  I believe this mixer is +3db and the other one I ordered similarly configured is a +7db.

The ZP-10514-S+ from MiniCircuits looks like THIS. (and costs about 2x as much as the ZX05-1L-+)

100 Mhz LO 2x Frequency Multiplier Idea:

The ZX90-2-13+ from MiniCircuits looks like THIS. Depending on how strong the OCXO output really ends up being it may be possible to use this device (with it's 11db loss) to 2x the 100 Mhz output of the OCXO up to 200Mhz.  The Mixers above should handle that frequency range.   This would make the output in my setup from all of this to be at 209Mhz which would avoid the issue of the FM Broadcast band on the output to the RTL Dongle.  This item is simple SMA type connectors (plug and play) so would be easy to test and the price is reasonable around $35.00.  (I haven't ordered this, but keeping the idea in my mind).  The reason this might be useful is if the RTL Dongle needs to be placed far away from the upconverter, the output of the upconverter would be 100 Mhz higher than the FM Broadcast band....and EASILY filtered out with a band stop filter if needed.  I honestly don't think I'd need to go this route, but it's something to consider, for many reasons.  Lets say you wanted to use a different OCXO frequency because it was cheaper or something, this might help you get he output into a range that's more to your liking.  It has a fair amount of loss so the LO would really need to have some decent output (I think) but anyway...I just didn't wanna loose this detail in case I want to play with it later.

Everything for this has been ordered, and now I wait.  I'll post updates and pictures as things progress right on this post page.

[MORE DETAIL ON THE BUILD]

(OCXO with Controllable Voltage Divider to Pin 1)

(subject to change, just a starting point concept)

After some reading I settled on using this OCXO it's a +2dbm 100 MHz 200ppb

I have several Mixers at this point.  I have an SBL-1+ which is a +7dbm mixer, a ZP-10514-S+ which is also a +7dbm mixer, and THIS ZX05-1L+ which is a +3dbm mixer.

After further reviewing the spec sheet for the OCXO I have it appears to me that the +3dbm mixer is probably the best choice of the bunch.  While I don't see a lot of difference in the Spectrum being displayed I suspect this +3dbm is better matched to the OCXO output. (I'm kind of guessing based on a very basic understand).