The B&W 800 isn't suitable for 160m or for WARC bands.
Victor 4X6GP
On Tue, Oct 19, 2021, 16:23 Steve London <n2icarrl@gmail.com> wrote:
> Thanks to all for the many useful comments.
>
> To answer a few questions:
>
> 1) The input and output SWR remain constant while the power output is
> drifting. Using ArraySolutions PowerMaster wattmeters to verify this.
>
> 2) The input drive power is 29 watts, and remains constant as the output
> power drifts.
>
> 3) The RF choke does get quite warm. However, it shows no sign of heat
> damage to the coil form, tape or wire. The only interesting thing about the
> choke is there is a small recessed "dimple" in the plastic form. Maybe a
> manufacturing defect ?
>
> 4) No other tank circuit components are heating up. The tank circuit looks
> pristine.
>
> I do have a B&W 800 RF choke in the junk box, but does it have enough L for
> 160 meters ? Where are the series resonances ? Maybe I could try it on 15
> meters to see if the original RF choke is the cause of the drift ?
>
> 73,
> Steve, N2IC
>
> On Sun, Oct 17, 2021 at 4:36 AM AJ <iamfromcanadaalso@gmail.com> wrote:
>
> > Hi Steve
> >
> > Few things.
> >
> > What is the input vswr doing when this happens?
> > What drive power are you using?
> > What is the grid and plate current doing when this happens?
> > The relay, caps or inductor in the circuit could be a issue.
> > As Kim asked is this into a dummy load or antenna or a antenna tuner?
> >
> > The thing is what you are saying is a most likely an issue with the
> > plate choke but you say it only happens on 15 meters which is strange as
> > that should be on 10 and 20 also on that amp.
> >
> > Have you had the cover off and looked at the plate choke?
> >
> >
> > Cheers AJ___ VE3HJ
> >
> >
> > On Sat, 16 Oct 2021 08:05:14 -0600
> > Steve London <n2icarrl@gmail.com> wrote:
> >
> > > I have a Commander HF-2500 Magnum, with a pair of 3CPX800's. Great
> > > amp.
> > >
> > > It has one quirk, and only on 15 meters. If the amp has been dormant
> > > for a while, the output power is initially low: about 1100 watts. Key
> > > down it gradually rises up to 1500 watts over about 10 seconds. After
> > > that, if I intermittently transmit, at least every 5 minutes, it will
> > > stay at 1500 watts. Only after being idle for ~30 minutes will it go
> > > back to the low output state.
> > >
> > > My thought is that something in the input pi network is heating up.
> > > However, I have accurate SWR/power meters on both the amp input and
> > > amp output. Neither the input power nor SWR is changing as the output
> > > power rises. As the power rises, the grid current drops, but the
> > > plate current is unchanged. Again, this is only on 15 meters.
> > >
> > > Suggestions ?
> > > 73,
> > > Steve, N2IC
> > > _______________________________________________
> > > Amps mailing list
> > > Amps@contesting.com
> > > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|