[Elecraft] AX1 Disappointing Performance

Mike Fatchett W0MU w0mu at w0mu.com
Wed Sep 25 22:19:18 EDT 2024


You have a small compromised sized antenna and QRP.  Maybe your 
expectations are a bit off.   Many people seem to do quite well with 
mobile setups using hustler/hamsticks.  If you are going camping how 
about a dipole or similar?  Toss a dipole in a tree for 20m is easy.  
You are wasting your time on 40m in Idaho and probably 30m.

W0MU

On 9/25/2024 4:57 PM, Dave (NK7Z) wrote:
> Hi,
>
> If possible raise the antenna higher.  Add more radials...
>
> A friend of mine has one of these and we took it out at a portable 
> station using a KX radio.  It was 6 feet above the ground, and had 6 
> radials on it, each around 20 or 30 feet long, sloped heading to the 
> ground.  We used WSPR on it during the big eclipse a few years back, 
> and it worked really well, hits all over the world on 20... Radials 
> are the key to making it work better. Being a shortened antenna it 
> will never work as well as say a 6BTV, but it will work well with a 
> decent set of radials.
>
> 73, and thanks,
> Dave (NK7Z)
> https://www.nk7z.net
> ARRL Volunteer Examiner
> ARRL Technical Specialist, RFI
> ARRL Asst. Director, NW Division, Technical Resources
>
> My favorite definition of an intellectual: 'Someone who has been 
> educated beyond his/her intelligence'.  Arthur C Clarke
>
> On 9/25/24 15:17, James Bennett via Elecraft wrote:
>> Several months ago I started building up a POTA station, including a 
>> KX3 (with internal tuner), the AX1 Dual Band Antenna, the AXE1 40 
>> Meter Extender, and the AXT1 Tripod Adapter. This afternoon I finally 
>> got the time to see how this antenna plays. I was a bit disappointed. 
>> Here is the setup:
>>
>> KX3 (with internal tuner), 25 feet of RG-316 with ferrites on the 
>> radio end, five foot tall carbon fiber tripod sitting in the middle 
>> of my back yard; no other resonant antennas on the property.
>>
>> The KX3 / ATU WAS able to find a match to the antenna on all the 
>> bands. At first I thought that was great. But being a bit curious, I 
>> disconnected the coax and hooked up my Rig Expert AA-55 Zoom. Ughhh. 
>> On 40 meters, with the long radial attached and suspended 4-5 feet 
>> above the yard, the antennas was resonant at 7.574 MHz - that’s a tad 
>> more then the +- 200 KHz stated in the specs. And quite ugly for 
>> where I wanted to operate: 7.052 KHz. So, I added the shorter radial, 
>> also up above the ground, going a different direction. NO CHANGE to 
>> the resonant frequency. Yes, I did have the AXE1 installed, and yes I 
>> had the switch set to the “20m” position.
>>
>> OK, let’s give 30 meters a try. I set the switch to “17m”, and the 
>> Rig Expert to 10.116 +- 5 MHz. Yikes - the thing was resonant at 
>> 8.070 MHz - very long way from 10.116. Adding the short radial 
>> changed the SWR at that frequency from 1.46:1 down to 1.33:1 but no 
>> change to resonant frequency.
>>
>> 20 meters didn’t fare much better. I set the switch to “20m”, removed 
>> the AXE1, and connected only the short radial. Minimum SWR of 1.34:1 
>> was seen at 15.330 MHz. At my desired operating frequency of 14.052, 
>> the SWR was 6.9:1. Not a very good SWR but one that the ATU can 
>> easily handle.
>>
>> 17 meters was just as bad. With the short radial it was resonant at 
>> 19.780 with an SWR of 1.15:1; at 18.116 it showed 6.83:1 SWR. Again, 
>> something the ATU can deal with, but…..
>>
>> While I understand that this is a compromise antenna and it isn’t 
>> going to be spot on on every band, I’m a bit frustrated in what I’m 
>> seeing here. With five watts output into those kind of SWRs, I’m sure 
>> I’m loosing quite a bit of my power in heating the coax and the 
>> modules in the ATU. I hesitate to go out on a maiden POTA activation 
>> with an antenna showing close to 7:1 SWR at my operating frequencies, 
>> even though the ATU “corrects” that.
>>
>> Any suggestions here? Is this “normal” for the AX1 and AXE1?
>>
>> Jim Bennett / K7TXA
>> Eagle, ID
>>
>> SKCC #10447T
>> B.U.G. #301
>>
>>
>>
>>
>>
>>
>>
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