I have always used this type of dipole because of it's ability to tune 40-10m and have never tried single band dipole's and wondered if anyone on this forum has had similar experiences and found a solution maybe a balanced dipole or vertical.

couple of things I have tried,

Turning off the power so only the radio is on, but not powered with battery as this will not be easy but can try if necessary

unplugging the coax to make sure the noise is coming from the antenna.

This is the antenna https://www.m0cvoantennas.com/apps/w...s/show/7856277

This is the rf choke https://www.m0cvoantennas.com/apps/w...s/show/2628660 ]]>

I have just ordered a winch to fit to the pole of the that supports my VHF/UHF antenna plus some rope.

Current I do have a 40/20 dipole made of ladder feeder but this might not be very practicle to mount due to the ladder. The front to back measurements of the house are about 10M I think, some pics are below. I plan on mounting the ends with large hanging baskets brackets and having the aerial in an inverted V shape. How does this sound? As you can see I am against a chalk cliff, I am very low down compared to surrounding land!

My main bands I'd like are 10M, 15M&17M(if possible) and 20m. I'd rather not use a tuner, but I could start off using my IC7000 and the matching tuner, long term I want to go back to my 706 Mk2 and I could purchase a tuner if needed.

Needs to be fed with coax.

Thanks and 73s!

James

Thanks.

Mike ]]>

NOTE: this work was started on the SDRplay Community Forum

https://www.sdrplay.com/community/vi...=4698&start=20

but I could not complete publication because of Forun closure. I am restarting the publication here.

PART 1

A single turn loop antenna is very simple to build. For the development shown below I have made a square loop with a side length of 88 cm, using wood planks from a discarded pallet. The advantages of a square loop are its small dimensions, better immunity from local man made noise and practically no cost. The drawback is that the antenna equivalent circuit is a resistor in series with an inductor and to get signal to the receiver you need (A) either a very high impedance termination, to avoid voltage drop on the equivalent series inductive reactance or (B) a parallel capacitor to resonate the inductance, but in so doing you lose the broad band capability. Solution (A) is broadband, but requires the use of a wideband amplifier up front, which can overload and generate second and third order intermod products in receive and make the antenna useless in transmit.

The proposed method is to use a special broadband matching circuit which makes the troublesome antenna series inductance disappear,

This method is based on original work by Philip R. Geffe (Simplified Modern Filter Design) who, as far as I know, was the first (in the fifties) to publish the idea that filter networks can be used not only for frequency band limiting, but also for broadband impedance matching. In his book Geffe gives tabulations for normalized elements of filter neworks working between different input / output impedances. Far more complete tables have been published later by Saal and by Zverev. For complete reference information, look here:

1. Handbuch zum Filterentwurf by Rudolf Saal, AEG-TELEFUNKEN, Berlin, 1979.

2. Simplified modern filter design, by Philip R. Geffe, John F. Rider Publisher, New York, 1963.

3. Handbook of Filter Synthesis, by Anatol I. Zverev, John Wiley & Sons, Inc., Hoboken, N.J., 1967

4. Normalized filter design tables, taken from Filter design handbook and downloadable as PDF here:

https://www.google.com/search?q=normali ... e&ie=UTF-8

Looking at the equivalent circuit of a small single turn loop, we see that it is represented by a resistor of a very low, sub-Ohm value, in series with an inductor. If we consider an useful frequency band extending from 3 to 15 MHz, we see that the median values are R=0.56 Ohm and L=4.6 uH and that the spread is relatively small. It must be noted here that I calculated the loop inductance with the formula shown below(*)

Now my idea is very simple:

a) if I take a simple Butterworth or Chebyshev prototype, say N=5 and

b) de-normalize it @ 15 MHz (or any frequency above the reception range I want from my loop) and

c) also de-normalize between 0.56 Ohm input and a convenient higher output impedance and

d) if the first series inductor has a calculated value higher than the antenna inductance,

THEN

e) I can incorporate the loop inductance into the value of the first network inductor and

f) Obtain perfect wideband match between 3 and 15 MHz without resonating the loop.

I shall now test the idea by calculation and if there is a significant number of simple networks that fulfill the conditions described above, I shall show them next.

(*) Inductance L = 0.008 * s * ln(s/l + 0.37942 + (0.333 * l/s)) = 4.29569 uH

Where:

L: inductance in uH

s: side length, cm = 88

l: coil length = wire diameter cm = 0.2

PART 2

NOTE: The theory of the proposed method becomes very simple in practice, when explained by a few schematics/illustrations, which I am not allowed to post at the moment, so I shall add them in future posts, when necessary permissions will be available.

Loop antenna equivalent circuit values in the HF frequency have been confirmed by MAMMANA antenna modelling performed by Phil, VK7JJ: note that the conductor diameter was set at 2.5 mm and we have a "real part" of Z which is the sum of radiation and of loss resistances. Calculated values are as follows:

Wavelength...........................80m.......... ......40m.............20m

Frequency fo, KHz..................3,550...............7,150.... ......14,150

Z, real part Ohm....................0.38................0.56... ..........1.1

Z, im part (inductive) Ohm......99...................207..............451

Inductance @ fo, uH...............4.4..................4.6......... ......5.1

Resonating capacitance, pF......453.................108...............25

The method outlined in the previous post is indeed theoretically possible, using data for polynomial filters with unequal terminations. In Reference 3, previous post, tables of lowpass element values are presented for filters accommodating not only in/out impedance ratios up to 1:10, but also prototypes matching a given impedance to open circuit (infinite Ohm) or to zero Ohm. This property is essential, because broadband loops made with thick conductors have real part impedances measurable in milliOhms, so the matching circuit must accommodate a termination approaching a short circuit.

In order to have a really low impedance loop, I calculated the parameters for a loop antenna with the same dimensions as the square loop specimen, but with much thicker conductor, bringing the diameter up to 15 mm, using the Magloop calculator spreadsheet Ver. 1.23. With this spreadsheet calculator we get the value of the radiation resistance separate from the loss resistance, so it is possible to optimize loop parameters before actually building the prototype. Increasing the diameter drastically reduces inductance and radiation resistance, while at the same time increasing potential bandwidth. Results are shown below: please note that resistances are now given in milliohms.

Wavelength.................................80m.... ............40m.............20m

Frequency fo, KHz........................3,550...............7,1 50..........14,150

Radiation resistance, mOhm..........0.5..................7.............. ...110

Loss resistance, mOhm.............:...34...................47...... .........66

Inductance @ fo, uH.....................2.8..................2.8... ............2.8

In the next part we shall look at a possible broadband matching circuit. ]]>

I have a 63 ft. end-fed wire antenna. It works well on 10-40. I have a tuner, but when I try 80m 2 things happen. First its noisy as heck. Second when I xmit, it causes issues in the house. My daughter can hear me in her speakers, my Google home beeps, etc.

I'm thinking about changing the wire to about 130 ft. Think that will help?

Thanks,

Darrell ]]>

Why is a longer antenna giving me worse performance than the OEM one? ]]>

Thank You!

Butch Reed

KF5NRP ]]>