When taking reflected power readings the slug should be 1/10 of the
forward slug value when testing a reasonably good antenna. So, a 100
watt forward slug would require a 10 watt reverse slug for reasonable
accuracy.
Unfortunately, the smallest HF slug Bird make is 25 Watts. That means
any SWR less than 1.4:1 (2.8% reflected power) is suspect with a 100 W
transmitter. It is a shame that Bird do not offer a 10 (or 5 W HF
element) and the one reason I moved to the LP-100(A) several years ago.
However, I would never think to take the LP-100(A) or microHAM SMΩRF
out into the field.
73,
... Joe, W4TV
On 3/19/2018 8:10 PM, JOE wrote:
I spoke to someone at Bird (when they were really Bird) years ago and I
was told that the Bird wattmeter is accurate to ±5% of top scale. This
means that a 100 watt slug can be off ±5 watts _anywhere_ on the meter.
So, a transmitter emitting 50 watts out, using the Bird and a 100 watt
slug, can read between 45 and 55 watts. That's why he said it was
important to keep the reading in the top 1/3 (highest) end of the
meter. This is where the error is less. When taking reflected power
readings the slug should be 1/10 of the forward slug value when testing
a reasonably good antenna. So, a 100 watt forward slug would require a
10 watt reverse slug for reasonable accuracy.
I retired my Bird 43 and the vast assortment of slugs for a Telewave
Model 44A wattmeter and never looked back. The drawback to the 44A is
it is limited to 20-1000MHz. The Bird would be good for HF use.
73, Joe, K1ike
Date: Mon, 19 Mar 2018 18:40:41 +0000
Always bear in mind that their odd meters (30 uA) are very non-linear and
measurements made using element ranges that fall in the bottom 1/3 or
so of
the scale are the most accurate. Overall, they claim to be accurate
to +/-
20 percent of full scale. HORRIBLE in
today's world!
FWIW ...
73!
K0PP
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [email protected]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [email protected]
