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Author Topic: High-SWR / Relays Chattering On Tuner, Never Completely engaging  (Read 3428 times)
KD6OZF
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Posts: 5




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« on: April 02, 2011, 07:57:51 PM »

Alright here is my dilemma...

I am working on a setup for my house which I can deploy with stealth at night and quickly remove it due to HOA restrictions. I have the following:

1) 100 ft cable of RG8X
2) G5RV Jr
3) Ultimax 100 Antenna
4) Yaesu FT-950 (just got it used a few days ago)

The other night I threw the G5RV Jr up in the tree, and got the legs out at about 45 degree angles from the ladderline. The center was raised about 25 feet in the air. Ran the coax into the garage under the garage door, closed it and hooked up to radio.  The radio would not tune, relays would only chatter.

Today I installed the Ultimax in the backyard. I had it in a flat top formation about 15' above the ground, it was horizontal. Hooked up the coax to that, did the same thing, but I got high swr alert on radio when it tuned, it was well over 3.

I do not have a grounding system in place other than the supply, since it will be deployed at night and quickly taken down. My question is, I suspect I might be getting RFI back on the feedline, and im wondering if I should go with an air choke line isolator, or is it suspected that I have another problem here> I do have some excess coax on the floor of the garage while I test, but I have made sure not to have this in any sort of loop. Im stumped guys, im on two strikes here, and trying to get something up that will at least work for the time being until I can engineer a super stealthy solution.

Any suggestions you have would be great!




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AC5UP
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« Reply #1 on: April 02, 2011, 08:03:40 PM »

The radio would not tune, relays would only chatter.

Most radios will do that when the power supply voltage is too low.

You're reasonably sure the power supply has enough moxie for the radio?
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KD6OZF
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« Reply #2 on: April 02, 2011, 08:10:28 PM »

Its a 35 amp astron, I believe it should have enough.
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AC5UP
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« Reply #3 on: April 02, 2011, 08:19:05 PM »

Hang a meter across the power supply and check the voltage under load just to be sure. If all OK, test the ATU into a dummy load. If all OK, double check the antennas and feedline.

BTW: If you installed the PL-259's yourself be aware that RG-8X melts *real* fast and I've had a very high failure rate trying to solder them.
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WB6BYU
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« Reply #4 on: April 02, 2011, 09:49:39 PM »

What is the SWR on the antenna without the tuner?
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NA0AA
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« Reply #5 on: April 03, 2011, 06:51:09 PM »

Your on board tuner is suitable only for antenna that are very nearly resonant,the G5RV does not usually come close to the 3:1 limit on your internal tuner.  I don't know the other antenna.

Either build yourself a resonant dipole or vertical, or get a tuner with a much wider range.

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W0NFU
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« Reply #6 on: April 03, 2011, 10:21:36 PM »

My first thought was addressed by others but I didn't see one important thing. Your rig isn't getting the proper operating voltage.

Place your volt meter to where the power is connected to the rig. Is it low? If so you might be experiencing Ohms Law. The gauge of the cable between the power supply and the rig could be too small and you're getting a voltage drop.

If this is the case, get a cable of larger gauge - I'd recommend at least 12 gauge or even 10 gauge.

73 - Larry WØNFU
Lake Forest Park, WA
larry_w@comcast.net
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NN4RH
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« Reply #7 on: April 04, 2011, 03:43:24 AM »

KG6WOU had it right.

The FT-950 internal tuner is only good for up to 3:1 SWR.

G5RVjr is generally higher than 3:1, except maybe on 10 meters.  

The chattering is the auto-tuner trying to find a tune, but it can't because the SWR is out of its range.



This has nothing to do with the power supply.
« Last Edit: April 04, 2011, 04:26:53 AM by NN4RH » Logged
W5DXP
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« Reply #8 on: April 04, 2011, 05:18:17 AM »

The G5RV antenna was invented when there were no WARC bands and most transmitters had tube finals  with built-in adjustable pi-network tank circuits. The Zg characteristic impedance of the tube circuits was thousands of ohms.

Today's built-in autotuners typically cover a range of ~17 ohms to ~150 ohms with a small amount of reactance.

Moral: One will be disappointed if one expects all-HF-band operation from a G5RV driven by a solid-state transceiver with a built-in auto-tuner. One will be lucky to get a narrow match on 2 or 3 HF bands.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
N1LO
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« Reply #9 on: April 04, 2011, 09:27:33 AM »

Sure sounds like either a shorted pl-259 connector or your tuner just doesn't have the necessary range.

I suspect the latter since you are using non-resonant, multiband antennas, despite the enticing claims on the ulimax website:
http://www.ultimax-antennas.com/services.html

Did you install a choke on the coax as recommended?

Two fixes for you:
1) Use the antennas you have and buy an outboard autotuner (much larger matching range than radio internal tuners), such as the LDG at-200
2) Use the radio you have and get on the air right now with a simple, homebrew dipole.

Sorry for your troubles - good luck.

- - · · ·  M A R K · N 1 L O · · · - -
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N4HRA
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« Reply #10 on: April 04, 2011, 04:17:20 PM »

I was having issues with my G5RV Jr with the rigs internal ATU, after doing research, I obtain a SGC ATU, connected the G5RV Jr Ladder line to the SGC ATU and the Coax back to the rig, I now can tune the antenna fro 10 - 80 with no problems. Now I tune the antenna and not the coax

Just my 2 cents


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NG0K
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« Reply #11 on: April 05, 2011, 05:29:52 AM »

What all the FT-950 owners said is true. 
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73, Doug - NG0K
KE3WD
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« Reply #12 on: April 05, 2011, 03:30:44 PM »

G5RV, the owner of that call was named Varney, stipulated in his writings that his design was indeed intended to be run with a Matchbox (antenna tuner) - and that matchbox covered a much wider range than the typical built in "antenna tuner" in today's rigs. 


73
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WB6BYU
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« Reply #13 on: April 05, 2011, 04:01:27 PM »

Actually Lou Varney, G5RV, recommended 75 to 90 ohm coax, and rather than an external
tuner the antenna was usually used with tube rigs that had a wide-range matching
network built-in.  This is also why there was a recommended coax length, to make sure
the impedance was higher than about 40 ohms, which was the lower limit on some rigs
on 80m due to the size of the output capacitor.  But such rigs often had no problems
match 300 ohms or so - one of the Johnson rigs was rated for 40 - 600 ohms.

There is nothing wrong with the G5RV approach as long as you understand that the SWR
will be high on several bands, and the feedline losses can be significant if you are using it
with a tuner in the shack.  Here is VK1OD's analysis of the G5RV:

http://vk1od.net/antenna/G5RV/index.htm
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