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The NEW Capacitance Hat Accessory (CHA CAP-HAT) is NOW available!!
http://chameleonantenna.com/Antenna Accessories/Antenna Accessories.html
Very simple to assemble the CAP-HAT will increase the antenna radiation and performance on HF frequencies.
A MUST for base station or portable antennas such as the V11, V12, V1L, V1, V22L or V2L.
$55 USD + Shipping
Cheers,
Carl
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kc7zwg said:
Carl,
I have HYBRID/V1/MIL combo and new CAP-HAT....
Can I put the CAP-HAT between the HYBRID & V1?
Or does it have to be between V1 & MIL ?
Martin,
The CAP-HAT must be installed as high as possible on your antenna as possible. It must be installed between the V1 and the MIL. The CAP-HAT increase the current distribution in the lower part of the antenna. The top end of the antenna,
the voltage is maximum and the current is zeroand at the
bottom end the current is maximum and the voltage is zero.
The radiation is maximum at maximum current. If the CAP-HAT is too low it CANT increase the current more as it is already maximum because it is located at the bottom of the antenna. You want to put the CAP-HAT where the current is the lowest to increase it.
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Capacity hats
All antennas have voltages and currents flowing through them
when they are operating. The voltage and current distribution
over them changes. For example, a dipole has a current distribution as shown in the diagram below:
A grounded quarter-wave dipole is just the top half of the
dipole in the diagram. Therefore, at the top end of the antenna,
the voltage is maximum and the current is zero (of course there
can be no current at the end of a piece of wire!), and at the
bottom end the current is maximum and the voltage is zero.If the dipole is then base-loaded with an inductor as
described in section 2 of the radios page,
the pickup from any length of antenna that the inductor replaces
will be lost. Note that this is also the part of the antenna
through whcih more current is passing (i.e. the bottom), and
therefore the loss of signal detected is even worse. Sometimes to
compensate for this, the inductor is placed half way up the
dipole, a method often used on car aerials which have a helically
wound section half way up. This leaves the inductor rather
vulnerable for our purposes however.Another way this is often compensated for is to use a capacity
hat. This is a disc mounted on top of the dipole which has a
large capacitance. This capacitance replaces a length of antenna
at the top of the dipole, where the current is low
anyway. Therefore the section of dipole directly below the
capacity hat has a much larger current, and the antenna picks up
more signal. You may have seen capacity hats implemented as a set
of radial wires from the top of the dipole in large broadcast
radio transmitters.The diagram below shows the current distribution in red with
the strength of the current represented by the distance away from
the dipole:
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I found that here http://robots.freehostia.com/Radio/Antennas.html but they talk a lot about it.
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Very interesting stuff Carl!
Just wanted to jump in and say that I have the CAPHAT installed at the top of my HYBRID between my HYBRID & V1 and it seems to help quiet the RX substantially as compared to CAPHAT between V1 & MIL.
I know it is not supposed to work this way, but over my damp PNW (Wash State) soil here, it is working wonders for my RX.... I am able to really dig down and "discover" some weak HF signals, coolest thing though is that they are very weak DX and when I can here them the combo can work them too!
In my tests I compare to a HYBRID+60ft Wire at 13ft sloping up to 35ft.
My DX setup is following:
- MIL Whip (top is 31 ft high)
- V1 Base (top is 20ft)
- CAP-HAT (15ft)
- Spring
- HYBRID (14ft)
- 15 Foot mast (1 foot in ground)
Tunes EVERYTHING even w/o tuner all is under 1.8:1
Most important is 20ft away from structure and HYBRID is 1 ft higher than roof of house, using 3 of COUNTERPOISE wires that are 8ft above ground, sloping down from 14ft @ JAWMOUNT
Just wanted to share my experience, the CAP-HAT has made a serious performace gain with my system!
Regards,
Martin
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Hi Carl. Recieved the cap hat the other day and got it installed. Nice piece of workmanship on "hub" that holds the rods. Really nice clean machining, a piece of art if you appreciate those kinds of things. I've got it mounted between the V1 bottom element and the mil whip above. The plastic washer fits nicely on the mil whip and fills that gap nicely and lends itself to strengthing the joint in my opinon. I am still playing around with it and with the condx we have its tough to find many contacts. But... UT7UJ from the Ukraine was calling today. I listened for an opening and I heard many US stations making a go for him, but he'd listen for a while and then continue CQ'n after a while - obvious that some stations he was either not hearing or not hearing well enough to make a go. So I tuned up a bit above him and went back to his frequency at 100 watts - bingo, first call QSO complete. This was on 18078 at around 19:26 UTC (13:26 MST) and was a CW QSO. I read with interest N4DOV's assessment that he noticed a difference in transmit once he installed the cap hat and was one of the reasons I ordered it. And to prove a point I guess, I really didn't expect to make this QSO - he was weak, fluttery (over the pole), and was not hearing many US stations - and from experience expected the same result as other US stations. But I made the contact and can't help feeling the cap hat made the difference.
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