John,
The original poster has a valid point, but how do you find a signal generator with different output impedances other than 50 Ohms? Please remember that Radio Amateurs use antenna systems that typically have impedances close to 50 Ohms at the antenna jack and 50 Ohms is what are published measurement methods are based upon. The measurement published is not wrong, it’s what it is at 50 Ohms.
The metering system in the Tecsun is based on 0 dBu (-107 dBm). It’s the specified reference point used by some receiver manufacturers, used in other radio services, whereas S9, (50 uV, or 34 dBu) is the reference point most Radio Amateur and short wave receivers use at 50 Ohms.
With a 34 dBu signal applied at the antenna jack, a considerably weaker signal (of 10 dBu) made the meter read 34 dBu. Many signal strength meters are “optimistic”, but ARRL Product Reviews have pushed the manufacturers in a friendly, competitive way, to suggest signal strength meters should read S9 with an input signal of 50 uV (34 dBu).
“Measuring field intensity accurately requires knowledge of the gain of the receiving antenna at the frequency of interest, which is an unknown in all but professional field intensity measuring equipment costing thousands of dollars”.
Yes, that is true, but how does that apply to the Tecsun? Radio Amateurs and the average Short Wave enthusiast are not professionals! All they need is a relative signal strength meter. They are not trying to read field strengths to measure broadcast antenna patterns to satisfy FCC requirements. The Tecsun is a low priced, portable receiver that has many good attributes; there is no need to overanalyze the signal strength meter. Most would be happy with a scale of 0 through 10.
Tune around and enjoy the bands!
73,
Bob Allison
WB1GCM
ARRL Laboratory Senior Engineer
Editorial Content Coordinator
ARRL Historical Collection Curator
ARRL, the national association for Amateur Radio™
225 Main Street, Newington, CT, 06111-1494 USA
Telephone (860) 594-0210; FAX (860) 594-0346
wdcx posted quotes from an ARRL representative above in this thread, hopefully with the prior permission of their author.
As for the comment posted there about overanalyzing the performance of signal strength meters included in receivers, is that of more importance than underanalyzing such performance?
Shouldn't the goal of such an analysis be the ACCURACY of that analysis -- whether or not that analysis was done by an ARRL representative, or a private party?
This is meant to be a humorous
piece of trivia. When I was young
(way way too young - too young
to have aquired any wisdom) I worked at
the ARRL in Newington from 1976 to 1977
and again from 1980 until 1986. I was
an editor for QST (very seldom), and had a few things
published in the magazine. (Very little.)
I also ran W1AW at night and weekends
during 1982 and 1983. (What a trip that was.)
Again, I was too
young to know anything about anything, but
I was there.
I thought it would be fun to mention it. It
was truly another life. During most of my
life, I have either lived in West Hartford, CT,
or Newington, CT - the next town over.
In my apartment on Main St. a few blocks
from headquarters - W1AW's
3.580 MHz CW
signal was 80 over 9. My grandmother's house
was at 399 Main St - about 1/2 mile in the other
direction. Oh my.
Bruce
Bruce
Here's an idea. Why doesn't everyone join The ALPB. Then, you can join our TeamSpeak meetings and acutally exchange ideas in real time with - speech! You can talk to each other.
I think this could bring some really interesting discussions to the floor.
Join The ALPB today!
I think this could bring some really interesting discussions to the floor.
In a manner of speaking.
Last night there were several added posts which are now missing from this thread...
That could be a symptom of website trouble.
There were some posts which didn't belong in the thread.
Neil