Tuesday, October 18, 2016

More Junk Box Rigs

FPM20 Rebirth of the hallicrafters FPM300
11/09/2016 ~ More progress.
 Today I installed a few more controls and am closing in on having the complete front panel in working order.

Pete N6QW

11/08/2016 ~ More on the Front Panel
 Since we already voted there is no guilt in working on the rig. The Tuning dial has been added and some more video of the rig.


73's Pete N6QW

11/07/2016 ~ Building the front panel.

Today I began work on the front panel. With my manual 3 axis mill (yes I have both a manual and 3 axis CNC mill) I made the cut outs for the display and S Meter. There is also a short movie. The final size will be 4 inches high by 10 inches wide by 12 inches deep.
FPM 20 Front Panel

Pete N6QW
11/5/2016 ~ More work and headed toward an enclosure! 
Today I did some work on the power supply board and that is now complete. It seems like the original designer's utilized several unique voltages on the main board such as 12.6 VDC, 3.6 VDC. 12 VDC and 6 VDC. I have a built a power supply board that now outputs these several voltages.
I have more or less decided on a box size (large it is) which will be about 4 inches high, 12 inches deep and 8 inches wide. There will be some blue paint involved. For those checking it is slightly less than 1/4 cubic foot in size.
I continue to make contacts and since have corrected the LSB BFO by moving it 50 Hz. I now can tune dead on 7.2 MHz and it sounds right!
Pete N6QW

11/2/2016 ~ The original FPM300

I have received a couple of inquiries wanting to know what did the FPM300 look like as a radio (before I got to it)? Wait no more. The photo below shows it was quite an attractive radio with a top cover that had toggle snaps on the side to enable quick access to the "innards". Once the snaps were released the cover simply rotated over and above the radio. It had a somewhat military appearance. [In the photo look along the lower right hand side of the case and you can see the toggle mechanism.]
Too bad it had some problems such as using a rubber band (I exaggerate it was a splined rubber band) for the band switching mechanism to gang control the band switch. Over time the rubber band failed and the band switch became inoperative. The VFO drifted and some of the suggested cures for several of the internal spur problems was the use of aluminum foil to provide shielding.
There were several variants such as the last gasp fix called the Mark III. These units tend to be overpriced on the auction sites. Today there are a couple of such listings on eBay and the one below has a buy it now price of nearly $250. If you can find one in a "garage sale" for $5 snap it up.
Pete N6QW
The FPM300 Mark I



10/31/2016 ~ Serious DX Action in the CQ World Wide Contest

No I am not a contester! BUT contests are a great time to make DX contacts which might not be available on a regular basis. To that end running full power (about 600 watts for the QRP aficionados) I made several Caribbean contacts, three with JA stations and one with a station down in ZL Land. [Keep in mind this was on 40 Meters from Southern California.] Admittedly I got 5X9 reports from all stations; BUT what is telling is that usually I made the contact on the 1st call. No my rig does not have DSP, nor does it have a noise blanker, and there are no funny equalizer  presence settings or dual watch; but it does have a very stable signal and is spot on in frequency. Did mention it does have a color TFT display?
What is significant is that the mainboard of the radio was built in the 1960's and after some horse trading cost me about $20. The rest of the hardware came from the junk box and it value is maybe around $50. So here I am with a $70 radio making serious DX contacts using nothing more than a droopy dipole whose center is 26 feet high. Just imagine what I could do with a pair of phased extended double bazooka antennas at 70 feet?
Now my mainboard does have speech compression and VOX so it does have a few refinements which I intend to fully explore. So OK cosmetically it now looks like a hunk of junk but in time I hope to run it through the "Juliano Blue" process and make it respectable. So my advice to any one reading this --keep your eyes out for the sow's ear --it just may turn out to be a silk purse.
Any one out there have a mainboard from a hallicrafters FPM300 that they would like to have move from their garage or shack? Email me and let me know. BTW there are many radios lurking out there with blown finals that otherwise are functional --you can give those jewels the same treatment and have a reborn radio.
Pete N6QW
10/28/2016 ~ New Power Amp Stage
 I have somewhat changed direction and added a 4 Watt Linear Amplifier Stage which uses a device I found in the junk box --a 2SC2075.  Had a board layout in my computer so about 10 minutes worth of work on the CNC mill and I had a new board. This is shown below. With 4 watts I can drive thru an intermediate amplifier the SB200 to about 600 Watts out. This is a signal that can be heard on 40 Meters all the way to the right coast from the left coast.
Schematic ~ the 2SC2075 is substituted for the 2SC2166 with no other circuit changes

The "As Built" amplifier ~ The metal case is the heatsink!

Looks like crap works like Hell!
You too can build rigs like this!
Pete N6QW


10/24/2016 ~ More refinements -- improving the power output.
Initially I set the carrier oscillator frequencies in the Arduino sketch to the values indicated in the schematics. The USB frequency seemed way off. A quick and dirty test is to set the mode to USB and normally speak into the microphone. The output was much lower than LSB. A second part of the test is to whistle into the microphone (the rig was connected to a dummy load) and the output noted. On LSB the whistle test produced about 1/2 the output on LSB as compared to speaking into the microphone. On USB the whistle test produced about 1/10 the output as compared to the LSB with voice.
Using a separate external oscillator for the carrier input I adjusted the BFO frequencies until the whistle test on LSB and USB was at the same power level and these in turn matched the output using speech. These values were much different from the schematic values. But then on closer examination of the circuit schematic for the BFO  both crystals had trimmer plus fixed caps connected across the crystals -- so the actual oscillating frequency was modified in production and different from the marked frequencies. In my rig the BFO is supplied by the Si5351 and the values are set in software. I suspect that I am really close but may be off by about 30 Hz on LSB, which I will further test to verify that hunch. 
These changes have resulted in greater output!  I switched the linear amp following the driver stage to the brick liberated from an Atlas 210X. Now I am easily seeing about 50 watts output and driving the SB200 produces about 450 watts on peaks. So we are cooking. This evening I had a QSO with a station in New York where I was running 50 watts and he had a KX3 cranked down to 1 watt. So with a modest power level you can have coast to coast contacts on 40M.
I am really excited about this rig! There are some plans in work to make this a two band rig covering 20 and 40 meters.
So far I have had about two dozen contacts with stations in California, Washington, Nevada, Utah, New Mexico, Arizona, Texas, Nebraska and New York.
Pete N6QW
FPM20 now working at 50 watts with an external amplifier!
10/23/2016 ~ The FPM20 is "Alive" and making QSO's
The rig went "live" on 10/22 and so far I have made about a dozen contacts. Some of the contacts were made using just the driver stage at 350 Milliwatts (this is the EMRFD variant with a 2N2222 and BD139). Several were made using the outboard SS amp running about 25 watts. One piece of DX was a QSO with a station in Nebraska. (KD7YUW) where I was running 25 watts.
This is how it looks but I desperately need to tidy things up.
This is the rig "as is" as of 10/23

This is the 350 MW driver stage and low pass filter.

Pete N6QW


Building a Junk Box Rig from a Commercial Transceiver Board.

In the photo below is a "breadboard" version of the FPM20. Essentially the heart of this rig is the main board from a hallicrafters FPM300 SSB/CW transceiver and the S Meter. I have added a 2N3904 Receiver RF amp stage, a band pass filter comprised of two 42IF123 10.7 MHz IF transformers padded to 7.0 MHz, a Si53551 providing the LO and BFO signals and a power supply board (the FPM used weird voltgaes0. Rounding this out is the SBL-1 that acts as a receive and transmit mixer stage. The audio output stage uses an LM-386-3.
In the video above the receiver was working but I got no output on transmit -- that is until I realized on the output chain (the final device on the board) consisted of a 40841 Dual Gate MOSFET. that has ALC applied to Gate 2. Upon close examination of another of the circuit diagrams I saw a note about ALC. On receive the voltage is "0" but on transmit with no signal applied the voltage was 6 volts supplied from the ALC circuit -- this was a negative ALC. As more signal (such as from over driving) is developed the ALC becomes less. I had applied no voltage to Pin 17 on the board so essentially the circuit was cut-off! I added a 5 volt regulator to Pin 17 on transmit and the circuit now works on transmit --and CW. The FPM 300 used a keyed tone for CW generation.
A new board will be built using my standard 2N3904 bi-directional circuit which acts as the RF amp on receive and the transmit pre-driver on transmit. There is sufficient output from the 2N3904 to fully drive the 20 Watt brick sold by CCI. This is why the rig is dubbed the FPM20. We are on our way.

Pete N6QW

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