Subj : RF Burn
To : Ed Vance
From : Roy Witt
Date : Wed Jun 25 2014 01:42 pm
Greetings Ed!
RW>> Right. I have a Bird Wattmeter using a 25watt HF slug, my
RW>> HR2510 shows no RF output while keying the mic in SSB mode. AM
RW>> or CW OTH, will show 10 watts into a dummy load (i.e. 1:1 SWR).
EV> I had to see what a HR2510 was, I thought it was a Radio made by
EV> Regency as my HR-2 is, but no, it's made by Unidin(sp?).
EV> -snip-
Uniden President series, and I have two of them. One in the truck and one
in the shack.
RW>> Or a field strength meter. to show any RF that may be there.
RW>> Key the mic and then go outside and sweep the area around your
RW>> 20M vee. Then key your 520 in CW mode and see what you get.
RW>> Better yet, try touching your inverted Vee at the place where
RW>> RF current is supposed to be highest. You should get a kick out
RW>> of that.
EV> And RF Current is Max at the Center Insulator of my 20M Inverted Vee
EV> that is just below my Gable Roof, Right?
A half-wave dipole schematic shows current max at the center of each leg
with a dip at the feed point. Or is that voltage?
EV> If that is correct I'd have to Key the Mike and Climb a Ladder to
EV> test that out, I Don't Think So, I'd have a Unmodulated SSB Signal on
EV> 20M for several minutes if I could do that test.
I've done that into a dummy load that shows nill at the wattmeter,
meaning that you would not have a signal on 20m unless you modulated the
radio.
EV> I can't do it anyway since the Co-Ax feed line isn't running from the
EV> Attic to the Basement where I could do it.
You could put a watt meter inline, either at the radio or the antenna.
EV> And before You Ask why not bring the 520 upstairs to do the test,
EV> Nope! -snip-
Why would you suggest that? I'd never do it either.
RW>> I just did a test of what I meant and my tests show this to be
RW>> true.
EV> Thanks for doing the test.
EV> That's suprising to me, of course your test was using a 25W MAX XCVR
EV> and I only have the Kenwood 520 to try here.
Remember that my previous statement was when I was using a 3w AM output to
the antenna that burned me. 25w would give me more of a burn and I'm sure
that your modulated SSB 520 could put out 100w, if you whistled. 8^)
