Skipp, It is not just a cautious road to travel; it may also be an unnecessary one. Since repeater coverage is primarily limited by its ability to receive the low-powered distant stations, 250 watts of transmit power may be far in excess of what is needed for a balanced system. Even at sites where the noise floor is very low, that much power hardly seems necessary.
Ironically, an increase to 250 watts from, say, 100 watts may result in reduced receive sensitivity if the duplexer must be improved to handle the higher power without desense. The power increase may allow the repeater to be heard full-quieting at a greater distance, perhaps a 20% increase, but may also reduce the ability of distant stations to be heard full-quieting by the repeater. In other words, an increase in power might result in a reduction in the coverage area. I'm not just making this stuff up- I have seen it happen more than once. At one Ham repeater site, the previous owner of a repeater had a TE Systems power amplifier set for about 150 watts hooked up to a Wacom 4-cavity duplexer. Even though the duplexer was perfectly tuned, it just couldn't handle that power level without some desense, and the coverage area was relatively small. When I took out the TE amplifier and fed the 15 watt driver directly to the duplexer, the coverage area ballooned to at least five times its previous distance. Some of the Hams who now were able to use the repeater from a considerable distance asked, "Wow! What did you do- triple the power output?" They were floored when I responded, "No, I cut it by a factor of ten!" I make no claim that my experience is typical, but I do assert that "More is not always better." YMMV... 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Friday, October 19, 2007 11:46 AM To: [email protected] Subject: [Repeater-Builder] Re: TPL amplifier - aka repeater operation at the 250 watt power level > Does anyone have any experience with the TPL 250 watt > 2-meter amps for repeater use? Yep... > (bugs, reliability, operating manual/schematic availability). > steve > WA4BVO Bugs - none Reliability - good Operating Manual - Normally supplied with unit at the time of sale. Schematic Availablity - Included within the manual although I have a number of TPL Amplifier Manuals available for free download off the www.radiowrench.com/sonic web page. A phone call to TPL with a valid credit card in hand always seems to produce results if you must have the exact manual for your specific amplifier. TPL-Amplifiers are about as generic as they come... repair is not a big deal if you're used to working with modest - moderate power rf stages. **** Sidebar: An increase to this relative higher power output level can be a cautious road to travel. A circulator and/or trouble control detection circuit is pretty much a must have. Little problems normally not an issue at operation below the 60/80 watt power level can quickly lead to an equipment melt down. There is very little fudge factor and always no free lunch with 250 Watt operation at/near 146 MHz. cheers, s.
