Tom, Yes - the spurs mentioned were not the ones created by running the power too low. Apparently, the 406-420 Mitreks had a separate issue which was not dependent on power setting, in which the local oscillator for the receiver would get into the exciter's multiplier chain.
I think almost any of these discreet-component PAs wander off the spec chart if you run them too far below rated power. My last UHF repeater was a 35w Mastr II, and it started getting pretty gritty below about 18 watts. 73, Paul, AE4KR ----- Original Message ----- From: TGundo 2003 To: [email protected] Sent: Monday, April 26, 2010 3:26 PM Subject: Re: [Repeater-Builder] Mitreks as UHF Repeaters? I ran a Duplexed 50W UHF mitrek @30W with a Fan on the heat sink for 5 years without a problem. I "Upgraded" that site to a full blown UHF Micor Repeater that is 75W. As expected on the TX the range is better, but the Micor is also a slight bit better on the RX as well. I will probably re-use the mitrek radio in a future RX site since I have it and the channel element. That being said, the Mitrek served me well and was a great way to get the repeater going. If I did Mitreks again I would use two radios, not because I had any problems, but because of the redundancy it would offer. TX or RX dies, just swap radios and your back on the air. As a side note to running a single duplexed radio, I never had any measurable de-sense, but I did get spurrs and crap when I tried setting the TX power too low. Its happiest at 50-75% of its rated power. Tom W9SRV --- On Mon, 4/26/10, Paul Plack <[email protected]> wrote: From: Paul Plack <[email protected]> Subject: Re: [Repeater-Builder] Mitreks as UHF Repeaters? To: [email protected] Date: Monday, April 26, 2010, 3:07 PM Ken, Thanks, appreciate the link. This document adds a few details to what I had on hand. Good to know the high-split Mitreks weren't prone to the spurs when duplexed. Also encouraging to read that the 30w radios will run 100% at 20w with the smaller heatsink. That's probably all the power I'd need in my application. 73, Paul, AE4KR ----- Original Message ----- From: Ken Arck To: [email protected] Sent: Monday, April 26, 2010 1:09 PM Subject: Re: [Repeater-Builder] Mitreks as UHF Repeaters? At 11:47 AM 4/26/2010, Paul Plack wrote: Ken, Correct, of course, but I'm assuming that in a 30w PA, smaller components not somehow directly sunk to the main chassis heatsink will reach their max operating temps in a very few seconds of key-down, and therefore have to be spec'd the same for intermittent duty PAs as if they would if they were in continuous duty. <---There are several components that are "common failures" in Mitreks used in duty cycle apps greater than it was designed for. One should read the following: www.ecso.com/ srca/modmitrek _files/mitrex_ mod.pdf Just sayin'.... ------------ --------- --------- --------- --------- --------- --------- --------- --- President and CTO - Arcom Communications Makers of repeater controllers and accessories. http://www.arcomcon trollers. com/ Authorized Dealers for Kenwood and Telewave and we offer complete repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp. net "We don't just make 'em. We use 'em!"
