[TowerTalk] Smoking Rotor Box

jmltinc at aol.com jmltinc at aol.com
Thu Jan 1 12:20:25 EST 2009

>Roger wrote:

>Routing the rotator cables with the coax is not a good idea, 
>particularly on 160.? I do it, but I'd still not recommend it.

Agreed, but he has no choice.

>Coax shield grounded at base of the tower?

I cannot answer that. My friend is a ham's ham. Been in the hobby since the 50's. Builder par excellence. Holder (and once holder) of several DX records on the high bands. I did not think to ask him this, as I assumed he does. However, I also presume that the RF has already gotten into the rotor cable on the way down the tower...

>Good Luck es 73

Thanks for the constructive reply Roger. I will ask about the grounding. It sure can't hurt.

-John, N9RF


jmltinc at aol.com wrote:
> Hello all,
> I have a friend (without computer) who has a Yaesu 2800 that has given him good service for a couple years. He works all bands from 160 meters through 10GHz. All of his amplifiers are QRO homebrew, of the highest quality.
An active ham without a computer?
> He recently constructed 2KW+ amp for 160 meters. All has been well since he put it on the air. The other day, he keyed up on 160 SSB and as he started to speak, he got a 'poof' from the Yaesu control box and a little puff of smoke. He immediately stopped. The rotor still works OK, so he opened it up and sees no visible burnt components (but has the tell-tale smell).

Ah, 160. The band of the eternal hot...well...everything.

I remember my first Field Day.  We had the Novice station (me) and 160 
at the same picnic table.  The 160 station (John, K8DMG) was a DX100.  I 
timed my Transmit/Receive switching to when he was listening. When he'd 
transmit everything metal on my rig was too hot to touch. It may have 
been RF but it felt like those switches were ready to start glowing. <:-))
> He scoped each rotor cable wire at the control box and there is plenty of RF on each wire on 160 and 75 meters at 100 watts. The amplifiers are separate for each band. The (smoking) rotor is for the?10 GHz?dish and the only commonality is that all coax (there are dozens) and?rotor cables all are routed together to the outside. There is one other 
Routing the rotator cables with the coax is not a good idea, 
particularly on 160.  I do it, but I'd still not recommend it.
Actually have a couple HF coax runs, plus 50, 144, and 440 runs, 6-pack 
control cable, two control cables for remote antenna switches, two RG-6 
to remote preamps at the TV antennas, and two RG-6 to the satellite dish 
through one underground conduit which I'd definately not  recommend, but 
I was lucky.
> Yaesu 2800 and two Tailtwisters that are not affected.
> Our thought was to choke out the 160 (as no other band has any effect) using a toroid on the rotor
 cable before it enters the box.
> Any suggestions as to core and turns?
> All suggestions are appreciated.
Coax shield grounded at base of the tower?
Good Luck es 73

Roger (K8RI)

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