Re: Using a HYCAS IF amp in the BITX receiver

Ashhar Farhan

as an aside, you mentioned using the feedback amps from the progressive receiver as drop in replacement. if you do have a spectrum analyzer handy, could you measure the transmit output, say on 28 mhz ssb? 
i was wondering this morning if they would offer substantially better spur reduction as their harmonic output would be lower.

On Fri, 11 Jan 2019, 04:46 Scott McDonald <ka9p@... wrote:
As you may have noticed, Farhan recommended on the HF Signals web site the use of the IF AGC system of Hayward and Damm, commonly known as a HYCAS, as a potential improvement for the uBITX.
Finally got around to trying this over the holidays in a uBITX receiver lash up, and was very happy with the results.  The HYCAS system works with a bit less gain up at 12 MHz, and I was seeing about -10 to +35 dB gain on the board with my particular build.  This is a fairly transformative modification.  I rarely found myself reaching for the volume or IF gain control in the three weeks I've been using it so far, and it sounds great.
I mention this only because Mike, G4JXX, mhadley157@..., has a limited number of boards (at $15 US plus postage) and kits left, so if you were inclined to experiment with this modification.  Mike told me he was thinking about having some more boards made if there was additional interest.  I've built 3, two at 9 MHz and the uBITX version at 12, and each one has fired up first time and performed well.
I have no connection to Mike other than as a satisfied customer, and had contacted Mike originally when Wes Hayward mentioned Mike as a potential source of a quality HYCAS board for another project I was working on.  So if you might be interested in trying this on the uBITX, you may want to reach out to Mike and check the status of his stuff while it's still available, or otherwise encourage his efforts.  Mike also had an ad in the back of the last issue of SPRAT with a bit more info.
And just a few other tracks in the sand for anyone else homebrewing uBITX hardware.
Kits and Parts offers very reasonable priced matched 12 MHz crystals that worked very well for the homebrew cw and ssb filters used for this experiment.  It may be unseemly not to buy 150 bulk crystals and sort them, but in the end, at a buck and a half a crystal, I got 2 nice filters for less than ordering a pile, and the filters turned out well.  Life is sometimes too short to match crystals, and 6 bucks in crystals for a 4 pole cw IF filter is another cost effective upgrade.
The WA8ISP and W0EB Raduino clones were both used in the radio, and both performed very well.
And if you are a Progressive Receiver fan, I tested the SBL-1 mixer/2N5109 post amps from Wes' original article as drop in replacements for the TIAS and homebrew mixers, as well as the product detector/ audio board.  They were, literally, drop-ins, and worked great.  The Progressive mixer/post amps have a few dB gain less than the TIAs if you leave the 6 dB pads in, but it was not an issue.
YMMV but just thought I'd pass it all along.

Happy building.
Scott KA9P

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