New Technology for 2020 ~ Software Defined Radios for Field Day

Preparing for Field Day ~2020

June 27, 2020 ~ FD is Here!

We had an amazing FD with six total contacts including one on FT-8. I know you are snickering; but that is the most contacts I have ever made on any FD in the last 61 years!

I spent my whole allotted hour for the operation with 25 minutes wasted on my tripod Vertical antenna. It just wasn't hearing anything so I simply tapped into my 40M Delta Loop and then the spectrum lit up. Thus that is six contacts in about 35 minutes. As I always say -- the antenna is more important than the rig. More proof of that today.

But there were some proof of concept pieces to my FD (Fun Day) foray. First and foremost I now have a way to totally power my RADIG from 12 VDC including the RPi3 and the 7" HDMI. Secondly I forced myself to permanently mount the RADIG on a metal plate versus the haphazard bread board. So those were two very positive outcomes resulting from FD.

Thirdly if I would really want to operate portable say from an outdoor park picnic table using my designer mask and the RADIG as a chick magnet, then a better portable antenna would be necessary. An End Fed Wire (EFW) would be a likely candidate.

I may take another run at operating from the back yard, other than some contest weekend. This also means rethinking how everything is packaged so it can be deployed and removed quickly. Some sort of portable cart with added built-ins would seem to make sense. Need to noodle on that a bit more.

This was a fun day (FD) but most likely would not operate Field Day (FD) again. 

Pete N6QW


June 26, 2020 ~ The New Power Supply has arrived -- The RPI3 and the HDMI now being powered off of 12VDC!

Wonders never cease as my power supply arrived today! For the power cables to the RPi3 and the HDMI, I took two 3 feet long USB to MicroUSB cables and cut off the USB end which then was connected to the Mean Well SD 25A-5 DC to DC Convertor which has an adjustable output. A setting of 5.3 VDC make all hardware connected to the buss act like happy campers. 

Can't wait until tomorrow.

Pete N6QW

June 25, 2020 ~ Final Actions for FD

Well I ordered the alternate variable 5 VDC DC to DC Convertor supply and got a shipped notice -- 4 days from San Francisco to Newbury Park a total distance of 340 miles. I have made that round trip in one 12 hour driving stint. But it takes 4 days using the USPS. Bottom line: It won't be here for FD so will have to use AC power for the RPi3.

I intend to run 100 watts with the SDR driving a small linear amplifier that formerly was the output brick for the Atlas 210X. It is compact and has the CCI LPF for just one band --40M.

Have been thinking about "snack food" -- you can't have a FD "op" without the usual snacks. I am thinking about some homebrew stuff; but haven't made the final decision. This is laughable as I only intend to operate for 1 hour; but snack food is one of the pre-requisites. 

Oh best check the ARRL rules on how I class myself. It will be single operator, single rig but AC power (darn) and definitely not wimpy QRP! Also need to check start times and duration. I will only be operating SSB (are there other modes?)

Set the portable antenna up yesterday after the lawn service finished, as I didn't want to have my ground plane caught up in their mowers. ( BTW Jose, Peppi and Luis do an outstanding job and indeed I am lucky to have these three individuals care for my yard. Always reliable and super careful it is so nice to see service providers who make a difference.)

I hope to add some detailed snaps of my portable antenna (later today) as that may be of some interest how I did it.

Stay tuned to this space. Oh very likely I will use my GoPro to film part of the FD op and so it will be available on you tube.

Pete N6QW

June 23, 2020 ~ FD Power Supply

The SDR RADIG With the Raspberry Pi3 and the 7" HDMI now totally on 12 VDC!     But There is a problem!

My goal was to have my FD station operate from 12VDC. I was able to power up everything from 12 VDC and then I noticed a small lightning bolt appear on the screen. 

That tells me there is low source voltage (not current) and sure enough the voltage was only 4.97 VDC. The Pi is especially susceptible to having low voltage input and anything less than 5 VDC makes it have heartburn. 

Unfortunately there is no output voltage adjust for this module. I will have to investigate further if t can operate this way (doubtful since the power on LED flickers on/off). Back to the Mean Well catalog. I think the HDMI can live with the lower source voltage but not the Pi3. Stay tuned.

Found a suitable supply. Same 9 to 18 VDC input but the output can be varied from 4.9 to 5.5 VDC and is rated at 5 Amps. It is the Mean Well SD25A-5 and is $22 from Jameco Electronics. That will cure the problem and It looks like with a Micro USB to USB C adapter it will work with the RPi4. So a bonus. 

I find there is an increase readership to the blog when I present techie stuff rather than trying to raise our social consciousness level. So Some Techie Stuff today.

The Problem: My RADIG which is the rig of choice for field day has some rather unusual power requirements. This is further compounded if you would want to take the RADIG portable or operate off grid. So lets us start first be examining the several required power sources requirements.

The RADIG has a built in fully functional computer and we have a choice of either a Raspberry Pi3 or and ASUS Tinker Board. These SBC's (Single Board Computer) require 5 VDC at typically 2.5 to 3 amps. Both have WiFi so if you are near a hotspot you can watch Netflix or You Tube while not on the air.

Next is the 7 Inch HDMI display which needs 5 VDC at about an amp for the backlit display. 

The radio part itself operates from 12 VDC with about a 400 ma draw on receive and up to 2 amps on transmit ( we get about 6 watts PEP).

If we drag along a 50 watt "leeneair" amp then we need about 12 VDC at about 10 amps. Man how that current adds up quickly. Of course we could do QRP (but that is like a trike with training wheels).

The 5 VDC requirement can be addressed using some very excellent DC to DC Converters from Mean Well. I have used these in other projects (such as the 2nd ZL2CTM transceiver) and NOISE is not an issue. These converters take in a voltage from 9 to 18 VDC and produce a consistent 5 VDC. This is great like when your main battery voltage starts to drop down to 11 VDC. 

See the nameplate for the Model Number and these supplies were Purchased from Jameco Electronics in San Francisco. They are on the web. The supplies are roughly 2 Inches square by about 1/4 inch high.

The RPi3 (or Tinker Board) are powered through a Micro USB cable. The same applies for the 7" HDMI. The RPi4 needs a USB "C" power connector.  So the plan is to use two USB to Micro USB cables and simply remove the standard USB end and that forms the connection to the 5 VDC side of the Mean Well. The primary side of the converters will be switched so you could actually turn off the 7" HDMI display to conserve power. 

For my application on Saturday I have a Astron 7 Amp Linear DC power supply and that will furnish power for the converters as well as the main power for the RADIG SDR. It will be close; but I will run some tests ahead of field day. Funny I have a Samlex 22 amp supply that is smaller and lighter than the Astron and I might just press on and use that supply. 

Later today I will add some construction photos of the SDR RADIG "power pack".

Pete N6QW

June 22, 2020 ~ Is my Coax Cut?

Is it me or have conditions been marginal? At least they appeared so over the weekend at my QTH. I have a metric that lets me judge the state of the band.

There is a daily "old coot" net somewhere in Arizona whose sole purpose is to complain about their many medical issues. We have gout, ingrown toenails and bit of prostrate trouble mixed in with COPD. Then of course there are bouts with flatulence. 

The metric --how strong or weak they are is telling about band conditions. Usually the lead station is typically in the S5/6 range. If he is in the noise then I know the band stinks. He was mostly in the noise this past weekend.

Hopefully we will have great band conditions coming up this next weekend for Field Day.

Got treated pretty well for Father's day including one special homebrew gift from my daughter. 

For 17 season's now I religiously watch the US Navy Cop Series entitled NCIS. When I was in the US Navy, I frequently worked with the NIS as it was called then. In fact they tried to recruit me as an agent when my service commitment was up. Carrying a gun everyday as I did when I was in South Vietnam didn't seem like a good path for me.

My daughter is likewise hooked on the series and the hero, Gibbs, played by Mark Harmon has a series of guiding principles called Gibbs' Rules. She went about imprinting Gibbs' rules on a T Shirt for my gift. Example Rule #51 Sometimes you are wrong. 

For those who attended the emperor's (with a small e)  fiasco in Tulsa this past weekend -- Rule #51 applies and regrettably if you do the math based on the ratio of US deaths to those infected and then apply the trickle down multiplier effect to 50% of those who attended (typically a 1:12 Ratio) you have 36000 infections and the number of deaths could reach 2000 just from attending the emperor's cluster bang! 

In about two weeks hope all those folks who get sick really thought it was great to attend, to not wear masks and to sit in some stranger's lap. The emperor doesn't care about you --he just wants four more years to be emperor!

Pete N6QW


June 20, 2020 ~ Checking SWR.

I replaced the 40M Hustler whip with a straight section of antenna so that I am loading an elevated whip 9 feet long. I added three 1/4 wavelength radials and used my homebrew tuner to bring the SWR down.

To make the SWR measurements I used a homebrew dual band (40/20M) SSB transceiver that will run 15 watts output.

The jump to 40 Meters was a pretty easy match where I got 1:1 and the background noise was loud. The 20M settings are yet to be determined.


I hope to participate in this years Field Day entirely from my small Southern California postage stamp back yard. There is a long history of my disdain for the yearly weekend long organized mayhem that afflicts our ham bands. This event, of course, is sponsored by one of the USA national amateur radio organizations. Thus my participation appears counter to that long held belief. Well actually not!

My interest is operating for at least one hour in the Field Day "clusterbang" and based solely to prove the viability of my entirely homebrew rig and antenna. 

Over the last week I have dug out quite a few of my commercial treasures such as the Collins KWM-2,  the SBE-33,  the Ten Tec Omni C and even the Galaxy V to evaluate their use. Then it struck me these older commercial rigs simply are not as good as the SDR Rigs I have built. Now that is a profound position to stake out!

Today I took the RADIG that was mounted haphazardly on a wooden board and integrated all of the boards and RPi3 on a metal plate. Nice! A compact RADIG. It was purely accidental that it all fit on the metal plate. Now I need to work on the power supply board where 12 VDC will power everything!

This was the RADIG before I installed it all on a metal plate. This will be the Field Day Rig.

My RADIG running off of the Raspberry Pi3 and Quisk gives me many of the functional features found in many of the current medium to expensive commercial SDR rigs --at a fraction of the cost. I have the waterfall, filter options, split operation and one of the most important --frequency accuracy and stability. I know that my RADIG is accurate to within 10 Hertz!

[A ham running a FLEX6700 with a GPS Synchronized Rubidium Frequency Standard scolded me that I should get on his frequency as I was 10 Hz off -- thus my claim!]

Thus I hope to share on this blog the details of the station I will be using. Firstly I will only operate on 40 Meters and possibly the source will be 12VDC as I likely will utilize the two 12 VDC to 5VDC DC to DC Converters (3 amps a piece) to run the Pi3 and the 7" HDMI Screen. That is another driver --getting everything to operate from 12 VDC. 

Today I am finalizing my whip antenna install as that will be the principal antenna. One of the original premises for Field Day was to prove the viability of hams to provide emergency communications during a disaster.

Now the focus is to showcase the latest megabuck commercial rigs that are promoted by the national ham organization. I guess the theory is --unless it is an ICOM 7300 or a YASEU FTdx101D then it is impossible to provide emergency communications. 

Let's all rise up and as Jack Black would say in the seminal movie "School of Rock" and stick it to the man and do it with homebrew gear!

Pete N6QW

We should also stick to the emperor (with a miniscule e) come 137 days from now. 

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