Antennas

In a previous post, I described how the ATB-75 Tiltover mechanism gave up the ghost in a high wind.  As a result, I’ve been off of HF for about 2 years.

Yesterday I ordered the last Hy-Gain AV-680 that DX Engineering had in stock.  It should be here tomorrow.

The next step is to see if I can find someone local who can fabricate a steel version of theATB_75 for me.

I’m looking forward to having this antenna up. There is now a 6M mountaintop repeater that is active in the area, and also it will allow mw to get on 80M.

I looked out the window this morning to see the 10ft mast for my Hy-Gain AV-640 vertical was leaning at about a 15 degree angle. I went outside and saw that the ATB-75 tiltover mechanism had failed in two places:

We’ve been having some high winds lately. It looks like the wind loading on the antenna and mast caused the upper bracket to tear at the bend (left photo). The subsequent movement then caused the upper bolt hole to hog out (right photo)

okay.

I’ve ordered a replacement ATB-75.  I’ve also decided to replace the Hy-Gain AV-640 with a GAP Challenger. My reasons:

• The AV-640 developed a high SWR on 40 meters. It had done so once before. I did not look forward to disassembling, cleaning, and tightening a bazillion screws.
• While the SV-640 worked very will sitting on top of a 10ft mast, it was HEAVY.  It took all the strength of my XYL and myself to tilt it down and up.
• I had a GAP Challenger several years ago. It was easy to assemble and maintain, and worked very well.

The GAP Challenger is now also on the way.  In the meantime, I’ll rely upon my 10-10M end-fed half-wave.

I ordered the EFHW-80-10 shown in my previous post.  And I ordered an EZ-Hang to get it up in the trees.

Long Long ago, there was a company named Palomar Engineers.  Their most famous product , a noise bridge, was inexpensive and had a lot of uses.  Palomar Engineers repackaged a portion of the noise bridge circuitry into a product designed specifically to allow you to tune your antenna tuner without putting a signal on the air.  That product was the PT-340 Tuner Tuner.

I strive to be a polite ham and due as little on-the-air tuning as possible.  A couple of weeks ago this PT-340 popped up in the QTH.com classifieds and I bought it, and I’m really impressed with it.

It certainly lets me tune my antenna tuner off-the-air.  The thing that really impresses me however is that I can tune my Drake MN-2000 Antenna Tuner much faster and more accurately than by conventional means.

With the the radio set to receive on the desired frequency, I turn on the PT-340.  It injects a white noise signal.  Then I tune my MN-2000 tuner to null out the white noise.  That’s it. (Then I turn off the PT-340, of course).

I’m surprised that modern antenna tuners don’t have this function built in.

Once again, a new hame asked about HF antennas and coax on Facebook.  And once again, someone said “Get RG-213 because it is lower loss.” Let’s Look at the specs (These specs come from the DX Engineering catalog):

As you can see:

• RG-213’s loss per hundred feet is only .4 dB less than RG8X.
• RG213 is considerably more expensive than RG8X
• RG213 is twice the diameter with a solid polyethylene dielectric, making it heavier and much less flexible.
• Both are Direct-Bury

I run 100ft of RG8X from my Drake TR-4C to my Hy-Gain AV-640 vertical.  The difference in loss is unnoticeable.

There ARE circumstances where RG8X is not the best choice:

• Your coax run is several hundred feet
• You are running high power
• You are operating an higher frequencies

In both these cases however, I would probably choose LMR-400 instead.

The replacement coax should arrive tomorrow that will hopefully fix my 6db loss.

In the meantime, I dug out my Ameritron RCS-4 Remote Antenna Switch.  I packed it away when I moved, and it occurred to me that I’ll probably be adding additional antennas in the future, so I should go ahead and install it.  I’ll mount the outside box (the upper one in the photo) on the wall adjacent to the antenna mast.

I’m getting antsy to get back on the air.

I woke up a couple of days ago after a windstorm to discover that the SWR on my Hy-Gain AV-640 on 40m was way out of whack (7:1). 30m was also bad. 20m was ok.(1.3:1). I walked outside and saw that one of the 40m capacity hat spokes was bent down and hooked on a 30m spoke. That explains that.

My MFJ-269 Antenna Analyzer also was displaying about 6db of coax loss. I’ve inspected the coax, expecting to find that a little animal had been chewing on it but I see no signs of damage. I suspect the heavy rains (9 inches in October) may be the culprit.

I’ve ordered replacement coax from HRO, and as soon as the ground dries out a bit more I’ll tilt the AV-640 down, fix the 40m spoke problem, and give the whole thing a good inspection. And replace the coax at the same time.

I’m getting the itch to get on 6 Meters.  The band has been open recently, so I’m starting to gather up what I need to put up a small 6M beam.  My neighbor gave me a 30ft telescoping TV mast for absolutely free. I’ll start looking for a used rotator.  I’m thinking of starting with this DiamondA502HB 2-element beam.

It’s such a please to be living in a place with no antenna restrictions and neighbors that don’t mind.