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Re: [Amps] AL 1500 P.O. Meter Function

To: "Roger" <>
Subject: Re: [Amps] AL 1500 P.O. Meter Function
From: "Fern" <>
Date: Sun, 4 Oct 2009 20:42:05 -0600
List-post: <">>
       I would suggest that it would be better to check the accuracy of the 
wattmeter if the amp was fed directly into a dummy load. The Hy-Gain 18HT 
Hy-Tower vertical is not necessarily a good 50 ohm feed (even though the swr 
indicates that it's in the ball park) and by adding some coax into the feed 
line, your amplifier was seeing a better load.It's quite likely that putting an 
antenna tuner in line that you will likely get more accurate readings. 

----- Original Message ----- 
From: "Roger" <>
Cc: <>
Sent: Sunday, October 04, 2009 8:12 PM
Subject: Re: [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.  
> If you have a reactive load the power readings and the power will be 
> different. 
> In cases like these it's best to check out the amp with a dummy load.
> Check out the antenna(s) with a good bridge. If the lode is reactive, 
> changing the length of the coax will change what the meter sees. You can 
> verify this with a bridge. 
>> 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.
> Simple watt meters, even calibrated ones, depend on the load being the 
> same resistance and non reactive for them to be accurate.
> 73
> Roger (K8RI)
>> Thanking you in advance for your thoughts.
>> Mike,
>> KE9AG
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