Batboard

I have a remote mount Spectra UHF that gets quite hot after about 30 minutes of transmit, especially on the part right after the mini-UHF connector. I am transmitting about 40W and using a duplexer. I've checked for cold solder joints and physical damage that might cause a mismatch but found nothing so far. Any idea guys?

Thanks

could be reflected RF going back into the radio, could be RF leaking, could be a bad PA, on and on... checking it out with a wattmeter or antenna sweeper and having an SWR will help in diagnosis

The 50 watt VHF and 40 watt UHF Spectras were bare rated to make a 90/5/5 level of usage. For this unit, 30 minutes of transmit could very quickly generate a fair amount of heat, especially if you are using a range three radio in the range two zone, meaning at 444, 443 or below.

When these things were designed, they were intended to cram ten pounds of :o in a five pound box and as a result, they skimped on heat sinking capability to give them room for the other stuff Take a good look at a 110 watt drawer, either VHF or UHF. In comparison to the X9000 or the Micor or even the Mocom 70, they don't have much of a heat sink, hence the warm feeling...and it ain't fuzzy either.

What you are describing is not unusual for a mid power Spectra. If there was an antenna issue resulting in reflected power, your radio would back off the power out. It sounds to me like normal operation

George

Thanks George and Jim. I was thinking about the duty cycle issue as well, but I shall get a SWR and wattmeter soon

I agree. After dealing with these radios for many years, it is soparant they were designed for a lower duty cycle. It really makes sense. Most users in commercial and public safety settings don,t realty transmit for very long periods of time.

The contractor Arlington county police used for the Gemini data radios velcroed them right to the Spectra radios in the trunks of cars. The heat was not able to disapate and they were blowing spectras left and right sending them in "OUT OF RANGE" or FAIL 001". Our shop has always told people not to put anything on the RF deck and give it plenty of room to breath.

Matt Tjaden
KI4IPP