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Author Topic: Longwire antenna performance / rig validation  (Read 13898 times)
KK4EAY
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Posts: 7


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« on: September 19, 2011, 04:31:27 PM »

I completed construction of my stealth(ish) antenna and I am not sure if it is performing poorly or if my radio is not performing correctly or if they are working fine and it is just inexperience.

The HF rig is an Icom 745 with a 30amp continuous rated power supply. The ground system is a rod linked to a steel basement window bay and a connected RF ground of radials totaling 550ft of 14 gauge wire held down by lawn staples. The antenna is a SGC 237 auto tuner connected to ground and feeding a 80ft longwire that rises to about 30ft at the house peak and slopes downward to about 10ft where it ends at my shed.

Tuning through the HF bands, 14 meters - 160 at night and 14 - 10 during the day I can go through most bands and hear nothing. I have tuned in about a half dozen ongoing communications and made my call during the breaks to see if I could be heard and nothing was responded to. The auto tuner appears to be working because I can see the SWR stay between 1:1 and 2:1 at 100w as I talk.

I am wondering if I could have a radio badly in need of alignment or if I have made some error in the antenna configuration, or maybe I picked a bad week to start HF use? I am still figuring out propagation determination so I don't trust myself to really understand if the bands are favorable or not.
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N4JTE
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Posts: 1168




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« Reply #1 on: September 19, 2011, 04:44:06 PM »

I assume you are trying to be heard from 10 meters to 160 meters on an end fed antenna.
1; How high and how long is the wire.
2; The radial system sounds substantial.
3; Concerned that an auto tuner can actually get a low swr from 160 to 20 meters, review your hookup.
4; Endfire antennas are one of the hardest antennas to make efficent, ie, be heard.
5; The bands have suffered from solar storms lately but not enough to exhibit what you are experiencing.
6; Seperate the radial system ground from your pipe thing.

Give us all a little more info perhaps we can help.
Regards,
Bob
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N3WAK
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Posts: 283




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« Reply #2 on: September 19, 2011, 05:55:48 PM »

Scott: 

Congratulations on your new license! 

If you want, we can have a sked tomorrow evening.  I live in Dover, DE, so we can try 40 or 80 meters if you want, or 20 for that matter. 

Over the years, I have done a lot of short wave listening, and listening to hams before I was licensed, using a random-length wire.  You should be hearing plenty of signals on your wire antenna--even if it's relatively short and relatively low.  So, it sounds to me like something is amiss. 

You could have a short in your coax...an improperly affixed PL-259...an SO-239 from your rig with a bad antenna connection inside...an attenuator that is on inadverte...ntly...a menu setting that is wrong...a lot of potential causes.  If you shoot me an email with your phone number, I can  give you a call.  tonykurl@aol.com 

Good luck!  73, Tony N3WAK
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KK4EAY
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« Reply #3 on: September 19, 2011, 06:12:54 PM »

I totally appreciate that response. I will email you about setting up a contact.

I did do some shortwave listening to troubleshoot the problem and I got mixed results. I am not hearing what I think I should, the big 10kw stations in Tennessee come in OK and I picked up some spanish and middle eastern stations but my expectations are rusty in the shortwave bands. I used to listen allot, about 10~15 years ago and I recently found that lots of former favorites had ceased operation, mainly due to the rise and dominance of the internet.

As far as the coax and rig go, the auto tuner came with a pigtail preterminated. I made up a 10ft cable (RG8) to connect the radio to the tuner using soldered PL-259. Continuity was verified shell to shell and pin to pin and there was no short. That said I may swap it out just to verify. I think I will also bypass the auto tuner and feed the ground and longwire directly to the SO-239 for RX only and see if their could be a problem with the auto tuner, it is new but you never know.

The 745 is a pre-menu era rig, there are no attenuators, and the RF gain seems to be working normally.   
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KQ6Q
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Posts: 1003




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« Reply #4 on: September 23, 2011, 11:59:00 AM »

Check the W1AW voice and CW bulletin and code practice schedules, listen on their frequencies at the times you know they're transmitting. That will at least give you a feeling for how well your antenna works on the various bands over a known path.
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M6GOM
Member

Posts: 1050




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« Reply #5 on: September 24, 2011, 12:42:49 PM »

I completed construction of my stealth(ish) antenna and I am not sure if it is performing poorly or if my radio is not performing correctly or if they are working fine and it is just inexperience.

The HF rig is an Icom 745 with a 30amp continuous rated power supply. The ground system is a rod linked to a steel basement window bay and a connected RF ground of radials totaling 550ft of 14 gauge wire held down by lawn staples. The antenna is a SGC 237 auto tuner connected to ground and feeding a 80ft longwire that rises to about 30ft at the house peak and slopes downward to about 10ft where it ends at my shed.

Tuning through the HF bands, 14 meters - 160 at night and 14 - 10 during the day I can go through most bands and hear nothing. I have tuned in about a half dozen ongoing communications and made my call during the breaks to see if I could be heard and nothing was responded to. The auto tuner appears to be working because I can see the SWR stay between 1:1 and 2:1 at 100w as I talk.

I am wondering if I could have a radio badly in need of alignment or if I have made some error in the antenna configuration, or maybe I picked a bad week to start HF use? I am still figuring out propagation determination so I don't trust myself to really understand if the bands are favorable or not.

Something is wrong. I have a similar setup but my wire goes up vertically and then is horizontal. I can work most of the world with it with 100W. From the UK this week on 10m I have worked Falkland Islands, Australia, India, Argentina, can get to the USA with no worries....

I think that you have the antenna the wrong way round. If it were me I'd have the tuner at the shed. I'd bolt a wooden pole to the shed to give me as much vertical as possible and then run to the house peak.
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WB6BYU
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Posts: 18464




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« Reply #6 on: September 24, 2011, 01:34:47 PM »

The SGC237 does NOT autotune unless you try to transmit though it. Otherwise you don't know what
frequency it is tuned for:  it could look like an open or short circuit on the frequency you are trying to
listen on.

If you transmit on 20m, say, and let the tuner adjust itself, you'll probably hear reasonably good signals
on the 15MHz SW bands, and perhaps at 12 MHz.  Similarly, tuning it for 40m might give you adequate
reception around 6 MHz.  Or not.  But without actually transmitting on the SWBC bands, you can't get
the tuner to tune itself there.

I suspect you'll hear a lot more SWL signals with the tuner bypassed, depending on the length of the
coax between it and the rig.
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AA4PB
Member

Posts: 15050




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« Reply #7 on: September 24, 2011, 03:54:11 PM »

The tuner should power up in the bypass mode (antenna connected directly to coax center conductor). It won't tune unless you apply RF power to it. Use CW or RTTY or AM to get transmitter output. SSB doesn't output enough power unless you are talking into the mike. Then its a bit slow because the power is always changing when you are talking normally.
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Bob  AA4PB
Garrisonville, VA
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