[amsat-bb] Re: TH-D7A Transmit Issues - Or Maybe Arrow Issues????

Edward R. Cole kl7uw at acsalaska.net
Wed Jan 12 16:34:19 PST 2011


Do you have any way to measure RF output power from the radio?  A 
power meter (or SWR meter) that indicates forward power.  If you do, 
measure power with Arrow connected to output of the meter.  Measure 
reflected power (or SWR).  If you have a dummy load connect it to the 
meter and test the radio with that and compare that with what you see 
with the antenna connected.

A duck is not a good 50-ohm load and depends on the field of the 
radio case to provide a good match.  So connecting a duck to a power 
or SWR meter will not give an accurate indication.  If the arrow is 
pointed at the repeater in the proper polarity it should indicate at 
least  couple s-units higher received signal than a duck because the 
Arrow has gain and a duck actually has loss.

Another thing that might "get" you with your simple comparison is the 
battery.  Can you measure the voltage?  Even though radios and 
antennas "seem" to be different a soft battery can drive you nuts 
with varying results.  If you have fresh charged spare battery try it 
with your comparison tests.

73, Ed

At 01:42 PM 1/12/2011, Zachary Beougher wrote:
>I did an additional test since my last email.......  I tried two 
>different radios (D7 and G71) using the same battery and I CANNOT 
>get into the local repeater now.  I came inside the house, put the 
>duck on, and I can hit the repeater fine.
>This would narrow it down to an issue with the Arrow.  Does anyone 
>have any ideas what might cause these symptoms?  I have not changed 
>anything with it.
>From: Zachary Beougher
>Sent: Wednesday, January 12, 2011 5:29 PM
>To: amsat-bb at amsat.org
>Subject: TH-D7A Transmit Issues - Or Maybe Arrow Issues????
>Since we are on the subject of satellite equipment, I have a question:
>I was on AO51 a bit ago, and I was able to get in okay at the 
>beginning using the THD7A for transmit, but as the pass went on it 
>was impossible for me to get in, even when there was dead 
>silence.  I tried the D7 afterward (using the Arrow like I would for 
>a pass) on a couple local repeaters, and I was having a hard time 
>getting into them, when usually I could hit them with a duck.  I 
>pulled the Arrow off and stuck the duck on, and I can get into all 
>the repeaters fine.  Keeping all of that in mind, I went back to the 
>Arrow and put a THG71A on in place of the D7 (same battery that was 
>in the D7), and I could hit the repeater okay.  I put the D7 
>faceplate back on, and it would not work.
>With the above information, I am getting indications of both an 
>issue with the radio and/or Arrow.
>Any ideas as to what the issue might be????
>Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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73, Ed - KL7UW, WD2XSH/45
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 144-1.4kw*, 432-100w*, 1296-testing*, 3400-winter?
DUBUS Magazine USA Rep dubususa at hotmail.com
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