[Moon] All I want for Christmas...

Mon Dec 24 09:32:12 CET 2007

Hi,

Just recalled another should do thing,

 as other wise will have diode noise out of the PA,

 will be huge noise generator and you will run in circles if you do not
realize this is the problem with poor receive,
 depending on the TX relay port isolation to receive port in receive..

In stand by mode for 8877 apply at lease 50+ volts to the tube cathode
so it is driven into complete cut off..

Most TRIODE amp wiring as shown the cutoff condition
  (cathode bias method)
 is dependent on leakage current to "all most" cut off the tube.

Will have micro amps of tube current in most amp design's to develop the
standby cutoff bias, will be a big noise generator..

The 8877 needs about + 50 volts on cathode???? as I remember,
 I suggest through a 1k to 2k resistor 2 watt or larger wattage??,
 don't recall now,
from a + 50 volt supply to the cathode side of the off/standby resistor,
this resistor will be shorted by the relay to ground in the TX mode,

 better if can use a SPDT relay at the cathode,
 just connect the resistor to the RX side of the relay and will not
short the 50 volt supply to ground in TX mode,

 The G3SEK Triode board is accidentally done so can use the relay on
that board that is used to short the cathode resistor and to apply the
50 volts+ already on the RX side contact's.

 to have a negative 50 volts to the 8877 grid,
 so it is in complete cutoff..
....................................................
MOVIE OVER SO, I'm done tonight all..............

tom W2DRZ

w2drz wrote:
> 
> Hi,
> 
> Just recalled when I lost a DOWKEY "402" years ago
>  (was $350.00 or so cost then),
> 
> We were going to run with RW1AW ??? think the was the station ?? off the
> moon, many years ago,
> well it was decided by the op that he wanted to use his rig as the
> driver,
> 
> That is fine,
>  well I used HV supply on and off to the 8877 sequenced as I have shown,
> 
> The driver was a bit hot on drive to the 8877,
>  after the smoke cleared
>  and we checked stuff it allowed the 8877 to output 3 KW to the coax,
> ?? not sure how much as it banged a 2.5 kw hard against the peg.
> 
> Ahhh, 4.5KV PA VOLTS @ over a amp of PA current as I recall the supply
> then used!!!!!!
> 
> But as I had not used cathode bias cutoff, was wired with a jumper
> disable for that and never wire to the sequencer, I depended on the
> power supply to be off/on when switched by the PA sequencer turn on.
> 
> There was a bunch of ON/OFF chattering do to a wiring screw up with the
> new rig, and flames came out of the relay, point was the PA was allowed
> to output power as the supply was still up on voltage when the ON/OFF
> sequencing occurred while the chattering went on......
> 
> I would hope you are not depending on the HV supply ON/OFF
>  (as I just described)
>  to keep the PA to be slow on power up,
>  but using a cathode bias cutoff system so it must be switch on by the
> sequencer and then make power normally...
> 
> By the way did work him off the moon as had a identical relay on my 432
> PA and robbed that relay after all the smoke cleared out and fixed
> things..
> 
> tom
> 
> Hugh VA3TO wrote:
> >
> > Yes Tom, I have a VE2ZAZ programmable sequencer
> > (http://ve2zaz.net/TR_Seq/Downloads/QST_032007_Sequencer_VE2ZAZ.pdf) in
> > service to:
> >
> > 1. switchover the relay
> > 2. switch on the amp
> > 3. key the radio
> >
> > I forget how much delay I programmed in off the top of my head.
> >
> > 73 de Hugh VA3TO
> >
> > w2drz wrote:
> > > Hugh,
> > >
> > > Big thing I see in your note is a BIG RF spike on TX??????
> > >
> > > Is the amp turn on in a sequence manner??
> > > a 4 stage is to be 3rd stage of amp on then the driver system is number
> > > 4 turn on, at that power would suggest a slow sequence, about 100 mill a
> > > second between 4 stages.......
> > >
> > > If NOT you will need a bunch of new relays????????????
> > >
> > > tom
> > >
> > >
> > >
> > > Hugh VA3TO wrote:
> > >
> > >> ...is a new RF relay.
> > >>
> > >> On Friday evening I rushed home from work to participate in the DUBUS 2m
> > >> CW event with hopes of working some new initials using my recently
> > >> christened h/b 8877 amplifier.
> > >> Something didn't seem right with the amp tuning and I quickly discovered
> > >> that the SWR was terrible. A continuity check on the TX feedline in the
> > >> shack showed a dead short. Today I climbed up the tower with my
> > >> multimeter and quickly discovered that the relay was the culprit. Some
> > >> slightly blurred photos below (too many Molsons' last night hihi !).
> > >>
> > >> http://home.cogeco.ca/~va3to/Relay/Relay1.jpg
> > >> http://home.cogeco.ca/~va3to/Relay/Relay2.jpg
> > >>
> > >> I thought the Dow Key transfer relay was good for 1700W at 144MHz
> > >> according to the datasheet but evidently not.
> > >>
> > >> So I'm looking for a replacement...doesn't have to be a transfer type.
> > >> A SPDT would suffice but it must be capable of handing at least 1500W
> > >> with a 12V or 28V coil.
> > >> I can pay using Paypal. Anyone ?
> > >>
> > >> Merry Christmas & Happy New Year to all !
> > >> Hugh VA3TO
> > >>
> > >> _______________________________________________
> > >> Moon mailing list
> > >> Moon at moonbounce.info
> > >> http://www.moonbounce.info/mailman/listinfo/moon
> > >>
> > >>  Please enter/update your standings:
> > >>  http://www.vhf-dx.net/top.html
> > >>
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> > >>
> > >
> > >
> 
> --
> 
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> 
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