[Amps] Attenuator needed

[Vic K2VCO]

I see what you did -- simple idea. I used some flat resistors that bolt to a heatsink,
each one rated at 20 watts. I don't recall, but I think they are called 'thick film'
resistors. Not the same as the metal film ones that you used.

Very nice work on your amp. I enjoyed the statement on your site that

> I always start with good intentions but after all the "mods" and "improvements", my
> projects usually look like the junk they were made from.

because I just determined that my 160-m tank needed a few more turns and, lacking a new 
piece of identical coil stock big enough for the whole thing, I just grafted a chunk of 
coil onto it! There goes the 'factory' appearance.


On 11/15/2010 1:09 PM, Larry wrote:
> Vic,
>
> I think you just got a bad resistor. I've been using similar resistors (from digikey)
> for my attenuators up to 100 watts and 144 MHz with no issues at all. You can see
> photos of one of them on the 3-500 amp topic on my web page.
>
> 73,
>
> Larry - W7IUV central WA - DN07dg http://w7iuv.com
>
>
>
> On 15-Nov-10 12:38 PM, Vic K2VCO wrote:
>> I made a 6 db attenuator for the input of my grid-driven amplifier in order to bring
>> the drive requirement up a bit and to provide a better SWR for the exciter during
>> tuning. I used some film resistors from Mouser. I suspect that these have a low
>> voltage rating, because one of them shorted after a few minutes of 10-meter
>> operation. They didn't show any sign of heating, so I think it was a
>> voltage/frequency issue and not simply overheating.
>>
>> Anyway, I need a 50-ohm attenuator that can dissipate about 40 watts and can be used
>> at HF. Anything from 3 to 6 db will work. I had a Henry solid-state amp that had a
>> couple of these, which bolted to the heat sink. Does anyone know where I can buy such
>> a thing, or how to make one from reasonably priced parts?

-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/