Cross Band Over Heat and Lockup AT-5888UVIII ???

[Tom Line]

Tried cross band repeat on my tri band last night on a local simplex chat. (was using my HT from the backyard) Worked great for about a 1 minute, had good signal reports, then locked up. The radio had powered itself down, and was really hot. This unit rarely gets more than warm on a simplex chat. Anybody got any ideas? I'm not a big talker so I'm kind of stumped. After it cooled for a couple minute, it worked okay for regular simplex use.
radio: Anytone AT-5888UVIII tri-band 144/220/440
antenna: Comet 333 tri band on the roof
left vfo - 146.565 right vfo - 446.565
left vfo - 25 watts right vfo - 5 watts
right vfo - required CTCSS tone set at 62.5 or 88.5 (forgot exact value)
(ht: UV-5R transmitting CTCSS 88.5 on 446.565)

 

[Tom Line]

I estimate it was transmitting at 5 watts for about 1 to 2 minutes, then at 25 watts for about a minute or less before it powered down. After it sat powered off for about 2 or 3 minutes, it would power back up, but I don't recall hearing the fan running even though the thing felt really warm still. So the fan looks like something to check at least.

 

[brandon7861]

When using a single radio as a crossband repeater like this, you are running it at nearly 100% duty cycle. Crossband repeaters work both ways, so after you get done talking and release it to listen, and someone else starts talking, that anytone is right back to work transmitting again. I don't know of any little radio like that which can do 25w continuously.

Great selling point, but not too practical on a busy repeater. You are going to have to get creative with the cooling if you want it to take such abuse.

 

[brandon7861]

If the users of the repeater can hear the 2m transmission, but just cannot reach it, you can cut your heat in half by using the crossband in only one direction and having the users set their RX to the main repeater so the crossband is only transmitting in one direction. That should instantly solve the problem. Otherwise, you will need to reduce power or add cooling.

 

[brandon7861]

Another thing you can try, if the distant users cannot at least RX the main repeater, is to keep both sides of the crossband operational, but lower the power levels individually to the lowest usable setting. If 5w gets you into the main repeater, there is no need to burn 25w in that direction. Likewise, if the users you are trying to tie in can hear 10w from the crossband, (or the main repeater itself), adjust accordingly. This is one of those situations where you cannot drive max power "just because"..

 

[Tom Line]

Thought I found an issue, but the fan wire is just smashed a little bit. I powered it with a 9volt battery and it spins okay.

 

[Tom Line]

Fan has never operated. Talked to R&L electronics and they just said it was less than 90 days so just bring it back and they'll give me another. Nice guys. Have had only good experiences with them. Next time I try it, I'll probably require a tone on the 2 meter input side (which my friends DON'T use) and just listen for 2 meter with the HT.

 

[Tom Line]

Gave the replacement radio from R&L a good workout last night and it performed great. Fan kicked up just like it's supposed to.