Lee,
I will experiment initially with 4 elements to increase the height, reduce
the capacitance, improve the ground, and use multiple wires. I also will
try 24 feet long aluminum pipes.
Ignacy
On Wed, Sep 20, 2023, 12:58 Lee STRAHAN <k7tjr@msn.com> wrote:
> 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@arrl.net>
> *Sent:* Tuesday, September 19, 2023 7:16 PM
> *To:* Lee STRAHAN <k7tjr@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@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@contesting.com> On Behalf Of
> Ignacy Misztal
> Sent: Tuesday, September 19, 2023 12:48 PM
> To: topband@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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