On 20 Jan 2001, at 11:26, Ken Kinyon - W7TS wrote:
> I have discovered that at least two of my bird slugs seem to be out of
> tolerance. My 2500H appears to read about 1/3 low.
> Can these be repaired or recalibrated?
> Thanks,
> Ken W7TS
The proper way to recalibrate a Bird slug is to use a calorimeter.
In fact, Bird even sells one. Another way would be to use an RF
probe and measure the RF voltage at a 50 Ohm resistor (dummy
load). There was an article in QST, I believe it was back in the 60's,
of a little project that would measure RF voltage, and by measuring
the voltage across its output, would give you a rather accurate
power reading. The author fit it into a 3" X 2" bud box. It also used
a small tube, and you had to plug it into 120ac.
Since the slugs are broadbanded, you should measure the error
across it's range and see which end (low freq or high freq) is worse.
Then you can calibrate slightly on that side of center freq.
As someone else mentioned, yes the skugs have a capacitor
compensation adjustment in them. It is located just slightly below
the center of the slug, right in the middle of the arrow --o-->
Good Luck,
Tom, N2SR
tacoll@ix.netcom.com
> Kenneth E. Kinyon
> 34 Princeton Circle
> Longmont, CO 80503-2106
> Voice/fax (303) 684-0037
> E-mail W7TS@Qwest.net
> ALPCA #8339
> ARRL-LM
> -----------------------
>
>
> -----Original Message-----
> From: owner-towertalk@contesting.com
> [mailto:owner-towertalk@contesting.com]On Behalf Of n4kg@juno.com
> Sent: Saturday, January 20, 2001 09:20
> To: TOWERTALK@contesting.com; aunwin@fgi.net
> Subject: Re: [TowerTalk] Ideal Antenna rejection characteristics
>
>
> F/B ratio is largely a matter of personal preference.
> Contesters in the North East USA like high F/B to
> reduce interference from the rest of the country
> while they cream us into Europe.
>
> Personally, from SE USA, I prefer a low F/B (10 dB)
> so that I can hear/work multipliers off the back of the antenna.
> This is especially useful for hunt and call type of operating.
>
> When I changed from a 2L Quad on one of my towers to
> a TH7 (which is normally parked on Africa), I found that I
> could no longer hear / work stations in the Pacific as I
> did with the Quad.
>
> On the WARC bands I use only dipoles and Long Wire
> antennas with ZERO F/B. This is only a problem when
> there is simultaneous Short and Long Path propagation
> causing a lot of echo that can make copy difficult. I have
> worked over 310 countries on each of the WARC bands
> with these simple antennas.
>
> de Tom N4KG
>
> On Mon, 15 Jan 2001 Arthur Unwin <aunwin@fgi.net> writes:
> > A review of presently offered H.F. Yagis show
> > in general >20 db for F/B or F/R ACROSS a band
> > One antenna manuf points to a a 38 db MAX which
> > one may assume means a steep fall off either side.
> > The Antenna Handbook seems to strive for even HIGHER
> > rejection ACROSS band which would appear that there
> > is some desirability for a HIGHER level of rear rejection,
> > but for whome and what level would satisfy those needs?
> > Do DX's have different needs than the normal
> > ham ? Is it a technical plateau preventing increases in
> > this area, or is it that further increases in this area would
> > be perceieved as a negative by some users?
> > Art Unwin
> > KB9MZ
> > aunwin@fgi.net
> >
> >
> > --
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> >
>
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>
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>
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