EMRFD Message Archive 8781
Message Date From Subject 8781 2013-07-05 08:04:11 KK7B 222.1 System for sale Still moving stuff around on the shelves, and decided that this one needs a good home too. I posted this one to the microwave list, as there are UHF and VHF contests coming up.
I'm staring at my museum shelf and an interesting 222 portable weak-signal rig is staring back at me. I realize I haven't used it enough in the past 5 years, as I have other ways of getting on 222. It has one of my original miniR2-T2-LM2 phasing direct conversion 2m rigs as a tunable IF, and a modular transporter for 222: a clean, zero gain transverter in a die cast box with Toko filter, 1.4dB noise figure preamp, and 1W power amp made up of commercial modules--QBIT amplifiers for the LNA and PA, little relays, and a Bird Low-Pass filter. Total system weight is about 6 lbs, and I think it will fit in a medium sized USPS Flat Rate Box, with padding. The relays need 24volts at a few hundred mA. I've dealt with that several different ways. For 222 only portable use, I made up a wiring harness with a little 12v gel cell in series with the +13.8 volt supply line, and that worked well for a contest weekend.
The 2m IF rig was featured on pages 12.33 to 12.36 of Experimental Methods in RF Design--it's the Wood Box version shown in figures 12.49 and 12.50. Pretty classy--I was making wooden jewelry boxes at the time.
The 2m IF rig has some limitations: no agc, but a front panel attenuator switch helps with strong signals; headphone audio output--I use it with an external computer speaker at home; and with the wooden box it has no shielding so is inappropriate for use directly on 2m--one of the quirks of an unshielded IF system with a BFO running on the signal frequency. As a tunable IF it's great--I've used it as a tunable IF from 222 up through 2304. Smooth VXO tuning plus and minus about 50 kHz centered on 144.100 MHz.
The modules are mounted on a wood board, with interface connectors to the 2m IF, so as it stands it's a plug-and-play 222 MHz 1 watt rig. I built up the system 15 years ago and it works every time I pull it out to make a portable contest contact on 222.1 SSB or CW. This is the one I usually loaned out as a rover, so it's pretty basic.
All the modules are connectorized, and I was planning to reconfigure it for a different application this summer, but before tearing it all apart I figured I'd offer it here for $400 in case someone wants an interesting 222 SSB-CW rig for the upcoming contests. Maybe not the cheapest way to get on 222.1 SSB and CW, but plug and play, something to talk about on the air, and it looks really nice on the museum shelf if you're into Radio Art with a publication history.