Home Antenna Considerations, Part 1.

 I am doing some considerations on a re-design of my antennas in and around the house. Right now I have a more or less functioning system, because during the pandemic I have not had the option of people coming to assist in antenna installations. 

The antenna system was due some maintenance the last 2 years, so now is probably the time to get started again.

This is my existing antenna system:

1) RX-ant:

- Active Mini-whip: 10kHz - 25MHz (needs some distribution/filter circuit(s))

- Indoor loop: 500kHz - 30MHz (lower than 500kHz w/amplification?)(needs distribution/filters)

- Loop on ground (30 - 160m, maybe MW/NDB bands w/ amplification?) (needs distribution/filters)

2) TRX-ant:

- R6000 (10 - 20m) (6m poor(RX only?)). In working order, but guy wires need to be replaced.

- Low 5B dipole (10-15-20-40-80m). Not very efficient due to the low height.

- V2000 (6/2m/70cm vertical). This is in working order.

- Corner vertical (mounted at the corner of the garden). This antenna has lost the top. I will have to check if the telescopic fiberglass mast has partly collapsed, or if it is broken. Originally this antenna worked in varying degrees on 160 - 30m, but it has certainly lost the 160m capability. Most definitely needs maintenance or re-design.

- Big Wheel, 2m (could possibly do 70cm) Omnidirectional, horizontal polarisation. This is generally in working order, but in rainy conditions it seems to deteriorate. Probably leaking, so needs maintenance.

- 10m 1/2 wave antenna. In working order.

- Low 2m/70cm vertical w/lossy cable. 

I am trying to make the antenna system as unobtrusive as possible, still with the functionality I want, so here are some requirements:

TRX Operation possible on following bands:

- preferably a possibility og making at least one QSO on 2200 and 630m. This may be tricky, but should be tested.

- 10 - 160m, reasonably well.

- 10m good (minimum as good as a vertical 1/2 wave).

- 4/6m needs to be improved (probably with Moxon, capable of running more power)

- 2m added gain, horizontal

- 70cm horizontal gain

- 23cm vertical and horizontal w/ some gain

- 13cm vertical and horizontal w/ some gain

- 9cm ???

- 6cm (maybe "14dB" patch array)

- 3cm 15/17dB horn or small (35cm?) dish

- probably some antennas should be capable of more than one band.

Diverse RX antennas: 

- Mini-Whip (2 pcs?). Will need distribution/filters

- Indoor WB loops for MW/HF. Will need distribution/filters

- Outdoor WB loop for MW/HF. Will need distribution/filters

- Outdoor loop for MF/LF(/VLF?). Will need distribution/filters

- Loop on ground antenna for MF/low HF bands. Will need distribution/filters

- other possible RX antennas may be considered, e.g. 4/6/10m RX antenna, 137/145/250MHz, 432MHz, 23/13/3cm monitor antennas.

I do have some ideas, but I think I will have to take yet another look at the garden and assess the possible solutions, so this is all for today.

Week End Activity, P.3: Loop on Ground Receive Antenna Experiment.

 The loop antenna adventure continues.

This time I revised the Loop on Ground (LoG) setup.

Some time ago I tried out a LoG made with field telephone cable. This cable is mostly made of steel wires, but with a few strands of tinned copper wire, in a 4x5m configuration. Probably not the best material for antennas, and the results were disappointing, and the experiment was halted. Now it continues.

After cutting the grass (first time this year, so it took some effort) I found some thin wire to lay down. It may be replaced with weatherproof wire later, but I got to test the system, this time the wire is a bit longer, the configuration is about 5x8m, so the highest band expected to work properly is 30m. I use pegs to hold down the wire, the type used to hold wires for robotic lawn mowers.

The box with the transformer had to be repaired, too, one of the transformer wires had disconnected since I last made the experiment.

I am testing with the IC-7600. Here are the first test results:

Initially the noise level all over the bands was poor, but winding part of the cable a round a ferrite rod near the radio improved that. A better common mode choke is desirable. Now I need even more ferrite (toroids and other stuff) for reducing RFI all over the house.

MW/LW sounds quite noisy and with low S/N reception. Not as good as the small NCPL (w/amplifier at the radio), and certainly not as good as the Mini-Whip.

160m sounds OK-ish with no preamp, not spectacular

80m sounds good, signals weaker than on the low hanging dipole, but noise lower, too. Almost equal, but I suspect that the 

60m sounds good, not spectacular, looks like it is a bit noisier than the dipole (using Shannon Volmet and FT8 as test signals), but then again, the dipole is not resonant on 60m.

40m weaker than the dipole, but sounds quite good. Comparable S/N.

30m looks quite sensitive, no resonant antenna to compare with yet, but it sounds like a decent receive antenna

20m: Looks like S/N is worse than the R6000. No surprise, as the Loop on Ground is too large for 20m

I suspect that the best band for this antenna will be 80m. 40/60/160 are probably OK with a better set of common mode chokes at antenna and radio.

On all the bands the noise floor of the receiver increased when the antenna was connected, so the IC-7600 receiver is sufficiently sensitive on all the bands I intend to use it for. It should also prove a decent receive antenna for use from 1.6 - 12MHz. I think I shall keep it and probably replace the wire, then get it closer to the ground, maybe a few cm under ground level. With some weatherproofing this should prove an interesting low band receive antenna in the winter season.

Amplified RX Loop Test and a Little Outdoor Antenna Work.

 This week end I have been active with antenna work.

Small Receiving Loop.

The first was a test using a low cost Chinese amplifier for the NCPL (loop).

The amplifier is actually "overkill", stated gain/bandwidth is 32dB/1-2000MHz. Not surprising, the gain is too high, both attenuators are in action on the FRG-100 receiver, and the base noise level (not interference), especially on 5-10MHz, is still very high.

Considering that the antenna is till tested indoors in the noise field I would expect things to improve when the antenna (properly weather proofed) is placed outdoors, but there is still one problem. The high gain causes intermodulation, maybe also cross modulation. I have not tested this, but in addition it is possible that the amplifier is oscillating in the UHF range. 

Which signals cause the intermod etc? I suspect it can be the MW broadcast band, but given the bandwith/gain of the amplifier it could be FM broadcast stations, too.

As I suspected this type of amplifier is simply unsuitable for such low frequencies, but I had to test it.

A simple 2 transistor with negative feedback is in my thoughts, along with a pre-selector. N1KPR has published a simple design that could be made on simple perf-board. 

Outdoor antennas.

The weather was pleasantly warm today, so a little outdoor antenna work was done. Since I do it all alone things may take a bit longer.

First outdoor thing was removing the lowered 6m half wave vertical antenna. There was a bit of rust, so the WD-40 was in action. This antenna was mounted on a satellite dish mount on the lawn, so this is now freed for other antennas. In addition, the cable was freed as well, and put to good use.

The 5 band dipole (10-15-20-40-80) had been connected together with the 4m vertical (now partly lowered) with a HF/VHF diplexer, which this was removed. The dipole is now connected to the old 6m antenna cable. Testing from indoors, the dipole/cable system seems capable of operating on 6m and 4m, so for the moment the dipole is used for 4m, because the 6m reception is quite noisy. The performance is expected to be quite poor on 4 and 6m, but until a better solution is available this will have to do.

The (partly taken down) 4m antenna is now connected to the old cable, running indoors, so a very limited 4m reception is possible, until another 4m(6/10/30m) antenna can be tested. At the moment only a transceiver capable of running a repeater is connected.

For now the 4m will be run on the IC-7300 with the dipole, and 6m on the IC-7600 with the V-2000 vertical.

It looks like the weather will be quite good tomorrow, too, so I may find time for more antenna work.

The Small Loop RX Antenna Adventure Continues.

Slightly updated.

 This is another attempt to achieve a good receive antenna system for monitoring different frequencies in as many (ham) bands as possible.

Stage one was the experiment with the Mini-Whip described in recent posts.

The active Mini-Whip did provide some decent to good reception on frequencies ranging from 16kHz up to 18MHz.

Not bad for such a small antenna.

Now the experiments have started for a small passive wideband loop antenna. The main idea is not new (at least 60 years old), but there has been a resurgence of interest since SDRs with good sensitivity and with reception capability on VLF have started becoming available at reasonable prices.

Looking at the "YouLoop" antenna made for use with the Air-Spy SDR I decided to look into this. 

This is in essence a "Moebius Loop" type antenna, a design invented in the 1960s, as far as I know. A version is available at the well known auction site, so I took the lazy way and purchased one, just to see what all the fuss was about.

This is the initial result of a quick comparison of the Mini-Whip and the YouLoop:

First I want to point out that the YouLoop as purchased is not suitable for outdoor use - no waterproofing.

This means that the Mini-Whip is mounted outdoors in one of the least noisy places I could find in my garden, furthest from houses, mine or neighbours' houses, and the YouLoop was hung inside the house, in the noise field.

Because the Mini-Whip is active the signal level is much higher than from the small loop. However, whereas some signals were audible with the active Mini-Whip and too weak to be heard on the loop, others were swamped in noise on the Mini-Whip and weaker, but clear with the loop. 

I am aware that the loop might benefit from a sensitive preamplifier, especially on low frequencies and with low sensitivity receivers. This I need to test.

Signals on the loop were a bit weak and noisy on medium wave, and somewhat comparable in S/N to the Mini-Whip on 1.8 to 10MHz. Above this the loop did not increase the receiver's noise when connected, indicating either insufficient sensitivity of the receiver (possible) or simply a too low output of the loop. MW was full of rather strong signals with the Mini-Whip, and considerable weaker (and more noisy) signals came from the loop.

I suspect that a low noise preamplifier at the loop will improve this, especially if a long cable is used. Oh, darn! more projects ;)

Having seen the results I decided to make my own (weather proofed) version of the loop. I already had some hula-hoops (yes the children's toy ones) stored and found a few of them. The first test will be a loop of similar size to the original "YouLoop" (My YouLoop clone). Using two lengths of RG-58 soldered together crossing the shield and inner conductor at the top of the loop, feeding the inner conductors at the bottom to a 1:1 transformer (type 73 binocular ferrite core), and connecting the shields together at the bottom. Here is a description already made, so I will not repeat everything. I will report back when the test has been done

I will have to check whether or not a connection of the feed cable shield to the common shield is beneficial wrt noise performance. I suspect it will be.

I have two more (larger) hula-hoops, so I intend to test a larger (2.5x or so) version of the loop for getting higher signal strength.

The loop antennas do have another advantage over the Mini-Whip: They are directional and have a null, making it possible to reduce interference/noise by turning the loop. For now I intend to use both the Mini-Whip and loop antenna, and switch between them to get the best possible S/N on a given signal.

Using separate receive antennas is beginning to take shape, and with the addition of a distribution system,  preselector/filters/amplifiers a decent propagation monitoring system, such as FT8/WSPR and/or beacon/QRSS monitoring.

Loop antennas.

Quick update on the loop antennas:

Since the excitement about the Es'hail satellite has resulted in spending some time preparing equipment, and some research on the internet, there has been only a little activity.

The shielded loops have been painted in green and brown colours, for blending in with trees and bushes. Also an unshielded single turn loop has been created. Some experiments with the single loop will be underway.