Monday, March 23, 2009


This is a subject I know very little about. I was hoping some of the fire breathing VHFers that occupy the denizens of SDR land would come forth and write a screed about the virtues of PowerSDR in the land of high performance VHF and satellite. Most of the guys interested in this area are pretty technically savvy so they can probably get the jist by just looking at the pictures (thank God)

My experience is limited to the 60's when I built a screen modulated AM 6 meter rig with a 6146 in the final and talked to all the TV's in the neighborhood. In the 70's I had a double extended zepp beam which was the brain storm of Russ Farnsworth (yes of the Farnsworth method) He was a blind ham that was living down the road from me in Arcola Il. This man was a wonder to behold. He was blind but he worked on his own gear using meters that had audio instead of visual readout. Russ had perfect pitch and he was a musician which was how he made his living. I think he went by "Blind Lemon Farnsworth" or something (just kidding) Russ had a little piece of property and he had a telephone pole for a tower. On the side of the telephone pole he had a rail road track. On the rail road track he made or had made a gzmo that could raise and lower his antennas for measurement. Hazer Schmazer he had a Farnsworth!! He also had a hand held field strength meter that outputted audio. He would run around his property taking measurements on his antenna range.

His beam idea was to use a double extended zepp as the driven element and to use a 1/2 wave element with the current nodes lined up behind each half of the double extended zepp. This means each parasitic element was made up of 2 collinear half waves and the 1/2 waves were separated by a 1/4 wave of insulation. So think double extended zepp with a bunch of 1/2 waves in front and behind each half of the zepp element. The result of this was a 2 meter antenna that looked more like a 6 meter antenna, AND with about 6 of these elements you realized 17 dB of forward gain. Cool idea!!! Russ was smart has hell. His feed also taught me about using open wire line on VHF and I have used it up through 432 with good result.

Anyway here is the transverter set up screen in PowerSDR. I high lighted 3 of the possible 13 VHF bands you could accommodate. As you can see each of these can be set up to run the transverter precisely. You can set that band spread (for example 144 to 146 or 144 to 148 depending on your transverter. You can also reverse the mixing scheme so if your transverter goes down in freq as your IF goes up in freq that can be accommodated. (I once converted an old Motorola mobile tube radio someone gave me to 432 sideband by mixing my Drake TX4's output onto the grid of a multiplier in the Motorola. I tuned the oscillator to 460 and mixed the 28mhz on the grid tuned the final to 432 and voila'. That kludge went in the wrong direction, but it was free and it got me on 432. This idea was cooked up by my old buddy Al Wolf K9SI)

You can set up in the case you have a RX only transverter and the RX gain, and the drive level etc. I have a TT 6 meter transverter and I used my SDR-1000 to drive that little bugger and this setup works like a champ. When I got the TT transverter, I didn't have a 6M antenna set up so I just used my 130ft 80M flat top. I made a quick little open wire tuner out of some wire and a couple of caps and had at it. In 15 minutes I was making contacts. My pattern was all up and down the east coast and down to SA so I made quite a few contacts with my 5 watts on my 80M antenna. I know this is all VHF heresy but like I said I don't know anything about this topic.

6M pattern of my 80M flat top

XVTR set up screen:

Here is a shot of what the radio looks like when you fill in some of those fields. The radio looks just like a 2 meter radio It keeps track of what part of the band you are in etc. You can set up the radio so that you can run full duplex for example like you might want to do for satellite work so you can tune yourself in the transponder etc.

Here is a shot of the antenna screen as you can see under expert mode VHF is fully integrated in automatically steering the signal out the right pipe, and turning on the right amp or preamp keying line.

The radio has built in a system to set up how long it takes between a PTT signal and how soon RF actually shows up on the pipe so you can tailor your preamp switching and all that into the signal flow. No need to burn out that nitrogen cooled FET or what ever!!

Station control is even more intense. In the days of the SDR-1000 there was a board designed by Tony KB9YIG (of softrock fame). It was called the UCB or universal controller board. Here is a pic of the board as implemented by KM0T These are shots from his site

Mike has done a great job of implementing the power of SDR into his shack and I strongly suggest you spend a little time on his web site. You see home brewing is NOT dead not by a long shot. The emphasis has just changed from build a RX to building a station.

The SDR-1000 used a proprietary I/O jack called X2. As such all peripherals for the SDR was a custom deal. Here is a shot of the X2 control panel in PSDR

You could control per band up to 6 things. I built an automatic antenna switch based on this arrangement. Click a band and ready to transmit. I also built a little fan control that slowed down the fan on RX and turned it on full on TX. I used pin 6. So all the pin 6 checks for all the bands were checked on TX if I wanted the fan to run high all the time (like for RTTY) I checked the pin 6's in RX.

The F5K has moved to something called the Flex wire which is actually an Phillips I2C bus

The bus allows for special chips to communicate with each other and can have a bandwidth as high as 3.4mhz. The bus is a master slave or master master arrangement and allows for things like pots and eproms and BCD to be addressed as well as switches and relays. If you can get a pot you can make a rotor or you can make an auto antenna tuner at the base of the antenna for example. There is a LOT you can do with this bus that is well beyond what we normally use in ham radio. The bus is a 3 wire affair but it can also be configured to a 2 wire affair. Ever want a wireless data port out by the tower? Check out this!

The first peripheral based on this bus is on design right now by Steve Nance K5FR and Phil Theis K3TUF. Here is a shot:

Note the LEDS It truly is alive!!!! Steve and Phil collaborated with Eric from Flex and Bob this weekend to allow the flexwire to be accessed form DDUTIL Cool!!! I just read a reflector note that this board is now talking to the UCB so things are heading in the right direction.

Read about this woner HERE This device will connect to the previous UCB as well as has multiple outputs that can control VHF transverters as well as low band stuff, as well as has an output that you can control discrete things like turning on your linear from a remote location, or switching the directions on your 4 square from the keyboard. The program that interfaces is called DDUTIL for which Steve K5FR is the author. Here are a couple shots from DDUTIL

And the Macro screen

It is through this program very complex station control manipulations can occur. For example you could have a macro that turns on your linear sets your band to 20M along with your linear to 20M tunes up your STEPPIR on 20, turns on RX 2 in PSDR and sets the VAC output to Skimmer to RX2 and rotates the beam. The VHFer, EMEer or Satellite enthusiast gets a very clear understanding of the macro idea's utility.

The DDUTIL board also can be controlled from a serial or parallel port on the computer so no need to access the flexwire unless you desire the special features the flex wire offers, for example ALC is being devised as a possibility. Flex wire offers the ability to send audio down the line as well as data. You can access A/D converters....hmmm maybe this is the solution to my daydream

Like I said, I'm sure I didn't do this topic justice. There is a ton of information underlying these notions, but what becomes very clear is how much you can play and experiment with your station with this system. It is all highly integrated and highly plastic. If you think home brewing is dead think again. It is so alive and well and vibrant its amazing. I often read EHAM articles about geezers complaining about the demise of ham radio. For me I was totally bored with ham radio. It was this SDR stuff that revitalized my interest. I think the reason people toll the death knell on ham radio is that they are the ones dying. It is their interest that has wanned, and they are merely projecting that onto ham radio in general. Sure magazines like QST have become brain dead. Who cares. I stopped reading QST 20 years ago (except I gave it one more try a couple years ago). It was like a soap opera, nothing had changed. It was still the same stupidity month after month. You too can make a mic holder out of PVC pipe!!! Hey Mabel did ya see QST has an article on building a 2M vertical??? This one was written buy some guy with a PhD in EE. What crap.

Its all out here if you want it, but nobody gonna spoon feed you. You have to get your hands dirty. The rewards abound.