Room for more? How do you know that? Are you guessing?
To answer your question; yes that was a guess. That is beside the real point here; but valid just the same. This thread was primarily written with the concern to go about understanding and possibly build a modest repeater. Perhaps even an emergency mobile repeater can be built and used with an external antenna, and the proposed freq are acceptable to the frequency coordinator. Thank You.
OK. So we understand that a duplexer
must be used to keep the receive on the antenna from desensing. Desensing is interference that can adversely affect the received signal when transmitting on the same antenna. Since the same antenna is both receiving and transmitting, the duplexer makes the TX and RX on the same antenna possible.
Building a 5/8 wave 2m GP antenna with an MFJ-259B can be also be done to save on cost - perhaps $5-$10 plus the cost of an N-connector. The Duplexer is $100 plus shipping from eBay (previously noted). I suppose some LMR-400 coax will work if we aren't going to exceed 50 ft working length length - that's about $75 with N-connectors installed. Let's say that I find a couple of older 2m radios with 50 watts output (<7 years old) at the local hamfest tomorrow for $80 for the pair; that would do just fine. Now, we are up to ~$260 in cost. Yes; I'm GUESSING that the duplexer can handle a 10 watt output w/o further desensing the receiver. The radio output heatsink can get beefed to have a greater duty cycle too for that 10 watt continuous duty.
Will the TX and/or RX radio need specific mods?
What do they need?
Now; what is next? Should the computer, sound card, and the Echostation software be considered next? I have enough old computer parts to put together a Windows 95 box for $0. I also have an old laptop that has Win95 already on it; this will keep the system portable too.
What about the IDer/controller? How does this hook up to the radios? Is it simple and comes with an instruction sheet? Is there a template that sheds more light on this? What about the cabling between the radios, the ID controller and the computer? Can the computer/Echostation software take the place of the IDer functions? Ideas/thoughts?
Moleculo said:
A way to ID - use a computer interface or use the ID-O-Matic from hamgagets for $25.
Using the computer as the ID interface running the Echostation software -I'll guess that the TX radio receiving the output from the receive radio thru the computer should have the VOX on so that it will transmit out. So that all that it would need is a cable from the output of the sound card to the mic input of the TX radio and the speaker output of the receive radio into the input of the soundcard. Perhaps an impedance transformer from the speaker output of the RX radio to the input of the sound card? Is that it?
Thoughts?
Here is a standard repeater layout FYI
http://www.eurekaboy.com/electronics/repeaterbuild.htm