On Thursday 10 July 2003 20:09, Brian Moran wrote:
> I perused the ~19 meg archive for "power combiners" --
> from my read, the suggestions were mixed for trying to
> sum the outputs of two HF amps. Has anyone tried the
> following?:
>
> Take two relatively-inexpensive amplifiers, say,
> heathkit sb-220's. Make sure that they both work
> reasonably well. With the hybrid combiner available
> from CCI (make sure to use those resistors in case of
> failure of one amp!), combine their outputs.
>
> Again, WITHOUT having done this, it seems to me that:
>
> With SB-220's at about $0.57 a watt (700 watts) or so
> OUT (CW), $~400 recent prices used (conservatively))
> they are seemingly inexpensive...
>
> Tuning would have to be done individually, then the
> amps switched into the network.
>
> Has anyone tried this?
I've heard of it being done on 432MHz. It's important to get the phase of the
two outputs close - if they're not, significant power goes into the resistor
in the combiner. I've no idea whether normal tuning of two similar amps will
deliver the same insertion phase. I'd suggest that the combiner termination
should be rated for at least half the expected output power so it doesn't fry
in the worst case. Final tuning could be done for minimum power in the
termination.
Steve
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