I own an Al-1500, and my buddy W7WW has two of them. We have
found that the wattmeter is extremely sensitive to
variations in swr or load impedance. It's a great amp
though.
Dave Hachadorian, K6LL
Yuma, AZ
----- Original Message -----
From: "MICHAEL HUGHES" <mhughes149@verizon.net>
To: <amps@contesting.com>
Sent: Monday, October 05, 2009 1:49 AM
Subject: [Amps] AL 1500 P.O. Meter Function
>I need some help. Upon receipt of my new AL 1500 I noticed
>that the Multi Meter P.O. "Power Output" function indicated
>1,100 watts output on 40 meters and similar low output
>readings on 15 meters. In all cases the load is a Hygain
>Hytower with VSWR at 1.5"1 or less on the frequencies
>tested. After talking to the factory they had UPS pick up
>the amplifier and it along with the tube were returned to
>Ameritron. I was given priority as it is a new unit. My
>contact at Ameritron couldn't find anything wrong with the
>amplifier and promptly returned it to me after asking
>question regarding my line voltage and whether or not I may
>have had the ALC connected. My drop is connected directly
>to the electrical box, 12 gage wire and the AlC was not
>connected. I asked the Technician on more than one
>occasion regarding the P.O. Multimeter and the accuracy of
>the Power Output and was assured that it was an accurate
>indication of power output.
>
> After receipt of the Amp it behaved exactly as it did when
> it left my home. Over the weekend I inserted an
> additional piece of Coax, RG 8214, approximately 24' long
> in line with the antenna and the amplifier and got
> significantly different numbers. I was driving the
> amplifier in all cases with a FT 1000mp Mark V Field with
> 50 watts indicated output power.
>
> The P.O. Meter now indicated somewhere between 1,500 and
> 2,200 watts depending on the band. All were checked with
> the exception of 160 for which I have no load at this
> time.
>
> I also used a scope, TEK 2235 connected to my EWE antenna
> to monitor the transmitted RF of both the driver and the
> amplifier. Using these numbers I extrapolated the gain in
> decibels, converted it to gain and multiplied the gain by
> the driver power (50 watts). Considering the drive, 50
> watts the results seemed reasonable, if not somewhat
> optimistic with power outputs approaching 1,500 to 1,800
> watts.
>
> My guess is that the power meter in the AL 1500 is really
> a "Relative Power Output" meter, not a Power Meter. The
> power meter reading should not be dependant on where you
> place the meter in the transmission line, or at least I
> would not think so.
>
> I am not complaining about the amplifier, overall, I would
> make the purchase again, based on cost/benefit.
>
> My guess is that this is a RF sniffer circuit which is
> good enough for a tune up process but not what I was
> expecting.
>
> If it is truly a watt meter then there is another problem.
>
> Thanking you in advance for your thoughts.
>
>
> Mike,
>
> KE9AG
>
>
>
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