Topband: HiZ 4-8 and beverages

[Lee STRAHAN]

Ignacy,
   From your description I think I see another problem with your RX array. If you have 4 foot ground posts buried 2 feet deep, you must have 2 feet of pipe inside the fiberglass. If your antenna wire is secured to the outside of that fiberglass that has the copper pipe inside you are actually creating a capacitor that will shunt intended signals to ground. The antenna wire is running parallel to the pipe inside the fiberglass causing this capacitance. In addition the fiberglass insulator has a dielectric constant of 5 or 6 which will cause this capacitance to be 5 or 6 times what it was if the wires were just parallel. You need to space the element away from the fiberglass where there is pipe inside  or eliminate what you can of the pipe inside the fiberglass to reduce this load on the elements. Because your thin # 14 wire elements are around 40 pF of source capacitance it takes very little shunt capacitance to drop the signal level. The Hi-Z amps of plus-6 vintage are around 12 to 15 pF input capacitance by themselves. Add to this a randomly chosen value of 25 pF of element/pipe load capacitance and you have lost 6 dB of your signal.
Thicker elements are a lot easier to work with in the long run as they have increased source capacitance causing less error from other capacitive loading from mounting arrangements and etc. ..
    This again suggests to me if you can that you should send me a couple pictures of your antenna element setup.

Lee   K7TJR   OR



From: Ignacy Misztal <no9e at arrl.net>
Sent: Tuesday, September 19, 2023 7:16 PM
To: Lee STRAHAN <k7tjr at msn.com>
Subject: Re: Topband: HiZ 4-8 and beverages

Lee,
For grounding I use 4 ft 1/2 inch diameter copper pipes. They are driven 2 ft into a clay ground, and a fiberglass pole inserts over the rest of the pipe. 18 ft of 14# copper wire.

I will try to add extra grounding and will make the vertical element thicker.

Sorry for not following with you earlier -  3 months of overseas travel.

Ignacy NO9E

On Tue, Sep 19, 2023 at 8:12 PM Lee STRAHAN <k7tjr at msn.com<mailto:k7tjr at msn.com>> wrote:
Ignacy,
   There are 2 things that come to mind with your array  elements as you describe them.
  The very first thing is when this has happened before it has been the result of not sufficient earth grounding from a ground rod mechanism at each element.
 This can result from insufficient ground rod size/length or the ground condition itself. Dry and or rocky soil is insufficient to cause a low impedance signal source to the Hi-Z amps and under extreme cases will cause a low frequency loss of performance. If this is the condition it can be remedied by installing 6 to 8 ground radials at each antenna element that are roughly the same length as the radiator itself. Space radials the same for all elements
   The second thing is your element description sounds as if you have used very small wire as the element itself at 18 feet length. These shortened elements exhibit a very small capacitance as the output impedance of the element itself. Larger diameters have a greater output capacitance which increases signal and also decreases the chance for differences between the elements.
   Personally I would add 2 or 3 more wires the length of each element to increase its apparent diameter. Then make sure there was a good earth ground under each element with and/or without adding radials.
 It also may be of help if you sent some element mounting and grounding pictures direct to me for comment.

Lee   K7TJR   OR



-----Original Message-----
From: Topband <topband-bounces+k7tjr=msn.com at contesting.com<mailto:msn.com at contesting.com>> On Behalf Of Ignacy Misztal
Sent: Tuesday, September 19, 2023 12:48 PM
To: topband at contesting.com<mailto:topband at contesting.com>
Subject: Topband: HiZ 4-8 and beverages

I have 600 ft reversible BevFlex beverages and recently I bought a used HiZ 4-8.
Both are about 300ft away from a shunt-fed tower for 160m and 4 sq for 80m.

On 80m, HiZ has a better F/B and hears slightly clearer than the beverages.
On 160m Hi-Z is deaf, with S/N at least 6 db below the beverages. A marginal copy on the Hi-Z is a clear copy on the beverages, and a marginal signal on the beverages is no copy on Hi-Z 4-8. Does not matter what direction. No big buildings around although some large trees.

My verticals are wires attached to 18ft telescopic fiberglass poles.

The noise level from Hi-Z is decent so the preamps must be working. All directions show the same background noise so probably the individual HiZ Plus amps are OK. The whole array had lightning damage before and was repaired by an associate of Lee.

I have a triangular Hi array at another QTH, very close to TX antennas and large trees. It has old ANT amps (not plus). Its sensitivity was never a problem.

Does anybody have an idea what could cause HiZ to be poor on 160 while being good on 80m?
According to reviews, HiZ should be pretty good on 160m.

Ignacy NO9E
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