[Amps] SWR meters

Sun Oct 4 21:45:11 PDT 2009

The DX Zone has a huge list of SWR meters.
But, it does not list my favorite, Autek WM-1 which has dual meters (not cross eyed) and peak hold, too.I have had no trouble with my 3 units, but u do have to be careful with the coax 13vdc power plug from unit to unit because occasionally they will reverse the + on the plug------between unit versionsAlso, the maker is grumpy.  I ordered my third one from Autek and asked for a 220VAC wall wart.  They sent the 115VAC one and said forget ur special request.
Things u want on a SWR meter-read true power regardless of SWR-remote sensor unit so your big coax does not drag the meter off the table.-dual meters-peak reading option.-Off switch.-range switch like 20 w, 200w, and 2000watt choices.
Happy Metering, 73

Charles Harpole
k4vud at hotmail.com 

> From: lists at subich.com
> To: mhughes149 at verizon.net; amps at contesting.com
> Date: Mon, 5 Oct 2009 00:26:35 -0400
> Subject: Re: [Amps] AL 1500 P.O. Meter Function
> 
> 
> 
> Based on the schematic of the amplifier, the PO function is 
> not a wattmeter but a simple capacitive voltage divider and 
> rectifier on the RF output.  A circuit like that has no 
> directivity and is easily confused by reflected power and 
> common mode currents on the feedline. 
> 
> If you are concerned about accurate power measurements, 
> get a good wattmeter and use it in a matched circuit - 
> SWR = 1:1 - and use common mode chokes between the meter 
> and antenna.  A capacitive voltage divider/rectifier will 
> only provide accurate readings with no reflected power to 
> "boost" or "buck" the voltage in the line.  For example, 
> if the SWR is 2:1, "power" calculated by using a voltage 
> measurement can range from 25% to 400% of the actual 
> power depending on the distance to/from the antenna (load). 
> 
> 73, 
> 
>    ... Joe, W4TV 
>  
> 
> 
> > -----Original Message-----
> > From: amps-bounces at contesting.com 
> > [mailto:amps-bounces at contesting.com] On Behalf Of MICHAEL HUGHES
> > Sent: Sunday, October 04, 2009 9:50 PM
> > To: amps at contesting.com
> > 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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> 
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