Hi Terry,
500 pf "doorknob" capacitors are not rated for carrying
significant RF current. They work great in high impedance
applications such as plate blocking capacitor but in low
impedance circuits they carry much more RF current than
they're capable of handling which heats them and causes
extreme capacitance variation.
Use an RF current rated transmitting mica capacitor, vacuum
capacitor or air capacitor and you'll be good to go.
73
Frank
W3LPL
----- Original Message -----
From: "terry burge" <ki7m@comcast.net>
To: topband@contesting.com
Sent: Monday, February 19, 2018 7:01:27 PM
Subject: Re: Topband: Conditions on 160m for ARRL Contest
I listened a bit on 40 and 80 mtrs last night and the night before on SSB. I
thought conditions were practically non-existent on 80 especially. 40 wasn't
much better. Turned the radio off again and worked on other things. Don't
exactly see any reason for it on the propagation page since the sunspots have
been at least a bit active (26,20,18, 15,12). Hoping for better conditions this
coming weekend during the SSB contest on 160. I know that FT8 activity is
likely to get some qrm around 1842 KHz.
All this talk about inv-L's has got me wondering about adding a second one
longer than my '1/4WL' one. But being so cold and the possibility of messing of
the operation of what I have now has kept me from trying a longer inv-L. That
and not being sure exactly how much and how high of voltage a variable
capacitor I would need. I do have some 500pF 10KV doorknob cap I can parallel a
variable cap with. And now hearing I might need longer radials. An acres and a
half only allows only about one 160 meter antenna at a time along with my other
ones.
But the talk has me thinking.
Terry
KI7M
> On February 19, 2018 at 8:22 AM W0MU Mike Fatchett wrote:
>
>
> I worked CT, CT3, F, JA, Kh6, KL7, UA9 for non carib or SA contacts. I
> missed much of the early Saturday night opening as I was gone.
>
> I was very happy to log the JA and UA9! Otherwise is was pretty poor.
> 80 and 40 were pretty lousy too.
>
> W0MU
>
>
> On 2/19/2018 2:21 AM, Roger Kennedy wrote:
>
> > > Well on Friday night I couldn't hear one single American station . . .
> > > even
> > though I heard a couple of Southern Europe stations working a few.
> >
> > Saturday night conditions were better, but signals were well down on what
> > they have been for the past few weeks.
> >
> > However, in the 3 hours I spent on the band (at different times in the
> > night) I did manage to work 61 American stations . . . including a few in
> > Brazil and the Caribbean.
> >
> > For future reference, here in Britain there are about 6 Navigation Beacons
> > between 1810 and 1818 kHz (they sound like the old Decca HiFix) . . . these
> > make copying weak signals VERY difficult, so a good idea to avoid this part
> > of the band !
> >
> > Roger G3YRO
> >
> >
> > _________________
> > Topband Reflector Archives - http://www.contesting.com/_topband
> >
> > > _________________
> Topband Reflector Archives - http://www.contesting.com/_topband
>
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