On 3/8/14, 11:57 AM, Sam Nabkey wrote:
I totally agree... I had a Hamtronics 220 repeater and I did exactly that...
After the audio mods it sounded really nice.
Since asterisk generates the ctcss, and will do limiting/processing, why would you not feed it into the modulator directly? The newer hamtronics PLL exciter boards are quite good. They don't do them as a kit anymore so build issues are not a problem (dear god how they were!) They are all SMT for the most part (less/no microphonics), and they switched the final transistor from case-collector to a case emitter (BeO insulated) so the final transistor does not have RF on the case anymore. It's direct FM, not PM. The only thing I use the amp/limiter for is the local mic, and I'm not going to be doing local mics on my repeaters going forward. All this said, hamtronics needs a small (BRASS) box they can sell to mount the boards in. I've made one out of PCB but it's not perfect and quite ugly. I detest wires soldered to the boards in an enclosure so I use some header pins and solder those to the feed-through filters between the segments. I remove the stupid phono connectors and put a proper SMA in place, and convert the unit so the PLL is always powered. Box Pics (SFW) http://gallery.keekles.org/d/28340-2/0308140155.jpg http://gallery.keekles.org/d/28343-2/0308140155b.jpg http://gallery.keekles.org/d/28337-2/0307141213.jpg The units are fairly trivial to sync to 10MHz, Put a SMA on the board and put a .1 uF chip cap in line where the TXCO used to be. I rip out the uP and dip switches and they are not needed (I'd asked hamtronics to modify their code to change R from /2048 to /2000 and they said it was going to take weeks and cost thousands to do it! Sucks but for $200 bux I got it going with a PIC 16f88). Couple this with a thunderbolt 10MHz GPSDO, and you have a frequency stability in the mHz (that's milihertz). Now I don't have a simulcast system online yet (working on the prime site now), but I expect everything should work. I could be wrong and have already been a few times, but it's a big experiment :) There are few commercial 220 repeaters out there, and even fewer that can take an external 10 MHz reference. You can convert/buy a micor to 220, but it's a 40 pound and 50 year old radio. By time you add in the cost of proper channel elements from ICM it's not worth it. The hamtronics exciter/receiver are "pure"; no extra crap, no stupid motorola design issues, if you need to modify it it's easy to get at basic parts. It's the basic building blocks, and no more. Sorry for the teal deer, but it's my thoughts on the subject as I take some shit for being a hamtronics supporter. -- Bryan Fields 727-409-1194 - Voice 727-214-2508 - Fax http://bryanfields.net