Tuesday, June 30, 2020

Because you asked

I get asked (a lot) how my system is setup.  Number ONE it's probably overly complicated, and under thought out.   But since people keep asking I'm trying to document it.

The SDR (Software Defined Radio) which I use is an SDRPlay "RSP2Pro" (no longer available I don't think).  The latest version that's similar is the "RSPdx" (there are several seller's but here is one I use)

My first priority is to keep my SDR's SAFE from high RF signals.  YES there is a fair amount of over-kill here.  NO you probably don't need to do the same thing.  It's just how I did mine and it's worked so well for several years now that I haven't had a need to change anything.

This same systems has worked about 70 EME QSO's on 6m.  So...it's safe to say that it works "pretty good".  Even if it's 'wonky' by your standards :-)  

The only reason I'm using the FTDX-5000 at this point is because it's what I own.  I've had it now for probably about 10 years.  It's 'just a transmitter' for the most part anymore.  I don't really use the RX chain other than to take what comes from it's internal T/R relay to it's "RX IN/OUT" ports.  That, and using it to PTT things.

The images below ARE clickable for larger copies.

First here's a basic block diagram.

This is where the SDR's are housed.  There's a small BPF not mentioned in the diagram above.  But it's shown in the two images below.  It's a simple "Mini-Circuits" 50 Mhz Band Pass Filter.  
I also use (between the Amp and the and the Antenna) a High Power "4O3A Bandpass Filter" for 50 Mhz.  Not only does this help for controlling out of band TX, but it also helps reduce the crap hitting the RX Port on the FTDX-5000.  This is one of those things that's probably not required for the RX but I think it helps.  I had it on-hand, so I use it.  Just like the FTDX-5000.
There's also a fair amount of circuitry that I've put in place to handle 'sequencing'  All of which takes <= 6ms to occur.  The FTDX-5000 PTT connects to a QSK-sequencer that has 4 ports.  The first output port connects to a 2ms relay that switches a 12v reed relay which controls a 5vdc line for a Mini-Circuits RF relay which can switch in 2ms also.  This relay dumps RX into a Dummy Load when energized.  Effectively placing the SDR's connected to the splitter on the Dummy Load.  This helps reduce the TX signals I create considerably!  The 2nd port then fires which keys the RF Amp.  The 3rd port is skipped currently and the 4th port triggers the FTDX-5000's "TX-Inhibit" line releasing the Transmitter to send RF OUT.  
This chain of events means that if the SEQ fails the TX will not flow out the amp.  Because I'm using the radio's built-in "TX-Inhibit" function.  It also means that RF Output only can occur when the SDR is listening to a 50 Ohm Dummy Load (safely).
AGAIN this whole sequencing section is my personal preference.  I suspect that it's not required.  I know that I've run this system without it and incurred no damage.
Using the RX IN/OUT ports to feed the SDR really is probably enough protection.  But like I said I've gone a bit over-kill.  
I would also suggest (not pictured in any of this) using a "Powered USB Hub" and a USB 3.0 port if you have one, and nothing less than a USB 2.0 port!  Using a Powered USB Hub helps keep the proper power on the USB connection.  In case you have a lot of USB 'things' connected - using a HUB insures that there's no voltage sag on the USB line feeding the SDR.
ALSO make sure you're power source for the Power USB Hub is CLEAN!  Don't just assume it is.  Test various power sources to make sure you aren't seeing Noise from the Power supply.
If you use Wired Ethernet...you'll probably want to consider wrapping it around a "Mix 43" Toroid Doughnut.  This will just about eliminate any stray RF if you're already using CAT 6.

The blue object in the center is an https://www.minicircuits.com/pdfs/SIF-50+.pdf

Friday, June 26, 2020

Arabian Peninsula FT8 decode times of day in FN54

After reviewing my Logs for places like: 9K2, A4, A6, A9, 7Z of 192 FT8 decodes since 2018 in FN54 the best times appear to be:

10z = 2
11z = 12
12z = 115
13z = 26
14z = 24
15z = 9

Wednesday, June 24, 2020

Big South American Opening

While this was happening it then opened up to Europe at the same time

Friday, June 19, 2020

High Power - RF Power Divider (Splitter)

MATH!!! - bet you never thought Math would be something useful in life did you?

I decided to try to build based on this: https://www.gare.co.uk/6m_antenna/divider.htm

But I soon found it pretty difficult to locate metric metal in the USA.  So I decided to use the calculations provided in the URL but to substitute with slightly larger common sizes found in the USA at your local hardware store.

Here is what I came up with based on their design:

  • Impedance of the quarter wave transformer
    • Z1 = Coaxial cable impedance = 50 Ohm
    • Z2 = Antenna's combined Impedance = 2 ports = 50 / 2 = 25 Ohm
    • = 35.355 Ohm
  • Impedance of a square tube with round center tube
    • Now calculate the impedance, Zo, of a square tube with round center tube
      • D = ID (inside dimension) of the square tube = 1.25" (inches)
      • d = OD (outside diameter) of the round center tube = 0.75" (inches)
      • This equates to an error of 0.36% from the ideal to the practical which is excellent
  • The length of the transformer is a free space quarter wave of 50.313 Mhz
    • Length = 300 / (50.313 * 4) = 1491mm (from N-type pin to pin) = 58.70 " (inches)
      • See NOTE1 below

So this comes out to:
  • Square tube dimensions 61.25" x 1.5" OD (1.25" ID) (PAY ATTENTION! critical)
  • The Copper tube is 3/4" OD (Outer Diameter - PAY ATTENTION! critical)
  • From Connector Input to Output N-Type center to center pin is: 59 1/4"
    • NOTE1: This is a deviation from the "Length of the transformer" note above.  I can't explain why/how I came up with this length because it doesn't match the calculated values above.  But this IS what I've used.
  • From END to center pin at Input is: 1"
  • From END to center pin at Output is: 1 3/8"

In the following photo I'm just resting the tube on the pins.  Before Soldering them.

Below - before soldering

Below - after soldering

UT9FJ - KN56 - Ukraine - Heard

Tuesday, June 16, 2020

9:52z 49.749.950 Video

Heard 49.749.950 around 9:52z - seemed to peak between 10 and 50 degrees.  Thought it could be China or Armenia but really no idea.  EU was working Asia at the time.  So may have been a skewed path via that @ 50 deg, and direct via 10.

Not real strong when screen shot these around 10:48z

UN6T - MN52 - Kazakhstan - Heard

20200616_090715 -16  0.4 2272 ~ K1TOL UN6T R-12 
 20200616_092645 -17  0.2 2271 ~ G4FCN UN6T RR73 
              20200616_092715 -11  0.2 2271 ~ G4FCN UN6T RR73           ^ 

UN9L - MO13 - Kazakhstan - Heard (while I slept)

and then....

Saturday, June 13, 2020

UN3M - LO61 - Kazakhstan - Worked #161

 20200613_140145   2  0.2 2102 ~ UN3M K1TOL -18               
 20200613_140215  -3  0.2 2103 ~ UN3M K1TOL -19               
 20200613_140215  -3  0.2 2103 ~ UN3M K1TOL -19            ^ 
 20200613_140245   0  0.2 2103 ~ UN3M K1TOL -19            ^ 
 20200613_140315   3  0.2 2103 ~ UN3M K1TOL -19            ^ 
 20200613_140345  -1  0.2 2102 ~ UN3M K1TOL -19            ^ 
 20200613_140415   0  0.2 2103 ~ UN3M K1TOL -19            ^ 
 20200613_140445   1  0.2 2103 ~ UN3M K1TOL -19            ^ 
 20200613_140515   0  0.2 2103 ~ UN3M K1TOL -19            ^ 
 20200613_141100 -16  0.4 1056 ~ CQ UN3M LO61              * 
 20200613_141116.965(0)              UN3M WW1L -16                
 20200613_141130  -8  0.4 1056 ~ WW1L UN3M R-08             
 20200613_141145.152(0)              UN3M WW1L RR73            
20200613_141200 -13  0.4 1056 ~ WW1L UN3M RR73           
 20200613_141230 -11  0.4 1056 ~ CQ UN3M LO61                 
 20200613_141615  -3  0.4 2168 ~ UN3M KA1R -15                 
 20200613_141645  -5  0.4 2168 ~ UN3M KA1R -15             ^  
 20200613_141700 -16  0.2 1056 ~ CQ UN3M LO61                
 20200613_141800 -21  0.2 1057 ~ CQ UN3M LO61                
 20200613_142200 -24  0.4 1056 ~ CQ UN3M LO61              * 
 20200613_142300 -17  0.4 1057 ~ CQ UN3M LO61                
 20200613_142730 -15  0.5 1056 ~ CQ UN3M LO61                
 20200613_142800 -20  0.5 1056 ~ CQ UN3M LO61              ^ 
 20200613_142815   5  0.3 1057 ~ UN3M K1SIX -11