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.

A More Expensive, But Not That Expensive, Portable Receiver.

On Ebay I purchased the Tecsun PL-660 portable radio receiver.

The PL-660 covers long wave (LW), medium wave (MW, AM band),  short wave (SW) up to 30MHz, the FM broadcast band (76 - 108MHz)  and the 118 - 136MHz air band (using AM). The receiver is also capable of AM synchronous demodulation and SSB  reception.

The receiver has a digital signal processing demodulator at the IF, and provides two bandwidths on AM reception, and that is a very useful feature, I found.

The receiver has an antenna input jack, specified to work on SW and the FM band. A test shows that it sooks like working in the air band as well. An external (active) antenna for air band reception should provide useful,  an FM antenna should be interesting, too.

The receiver uses 4 AA size cells for it power supply. These can be 1.5V (alkaline) or 1.2V rechargeable cells. I used a set of Eneloop (NiMH) cells, and when fully charged, they showed "battery full" on the indicator, and also tells that I was using NiMH batteries. It stayed like that throughout the testing of the radio.

The air band would have been perfect for my propagation monitoring if the VOR band 108 - 188MHz were included, but I reckon that I could use a low cost SDR for that, if need be.

A quick test showed that the sensitivity of the receiver is quite good on MW,SW and FM, as well as the lower part of the air band. The higher part of the air band seemed to lack gain, maybe due to bad tracking of the input filter.

Speaker quality sounds quite good for its size.

To me, however, it sounds like the DSP (demodulator/IF filter) could be improved, I detected some distortion, especially with somewhat noisy signals, that I never noticed on a fully analog receiver, or with my Icom IC-7300 and similar SDR/DSP heavy radios. OK, I guess that I got what I payed for ;)

I do think that this could be improved in later models. I suspect that it is not possible, or at least not easy, to update the firmware of the PL-660.

The accompanying power adapter, however was a bit of a disappointment. The adapter from US plug to EU plug did not fit into a mains socket, and just bent completely out of shape, no matter how carefully I tried to insert the plug(adapter). So I could simply not test the power adapter. I should probably try to find a suitable adapter, or simply cut the cord with the plug for the radio and make my own 6V power supply for this receiver.

All in all it is a nice and usable addition to my receiver park, I like monitoring a lot of frequencies simultaneously, to get an idea of the radio propagation conditions, be it on LW,MW,SW or VHF/UHF/Microwaves. The previously purchased "cheap" receiver is no more than just a toy, unlike this one. 

Maybe I should make another post or a few, about the setup I use for propagation monitoring. I think, however, that this should be at a later stage when I have completed more of the system.

Portable Radio on the Cheap.

I have tested the Retekess radio. All analog. Price about 20 GBP on amazon UK. I wanted to play a bit with a modern cheap radio with short wave.

Power supply is a single 18650 cell, rechargeable in the radio via a micro USB connector. I like that. The cell can, of course, be replaced. 

The radio covers FM 88 - 108MHz, SW 8 - 18MHz and MW 530 - 1710kHz.

FM works mostly nicely, tuning is OK, a little fiddly, but doable. Good sensitivity.

MW tuning quite fiddly, sensitivity poor to mediocre. Probably due to a small ferrite antenna.

SW: One band 8 - 18MHz. practically impossible to tune to a station. Sensitivity barely sufficient with the built-in telescopic antenna.

Very nice sound from the speakers, surprisingly good for such a small radio, will probably be in use.

The radio, as it is, is unsuitable for short wave reception, it is essentially impossible to tune it to a single station, mostly due to backlash in the tuning system, and due to covering 8 - 18MHz in a single band. It is essentially just a toy for SW reception.

I might be possible to make it tuneable on SW with a fine tune addition, but the modification might not be fit into the casing.

All in all a somewhat decent portable FM receiver with a medium wave performance only sensitive enough for local reception of strong transmitters.

Short Wave (Active) Hula Hoop Antenna.

The radio construction activities have been halted in the Christmas/New Year period, other activities have taken over. This week the ham radio activities are slowly beginning again.

The 1MHz - 2GHz 32dB gain Chinese LNA has arrived. Still waiting for LNAs for 10/100kHz - 2GHz, so the first loop tested will be for short wave.

Tried the electric connector box for the single turn loop RX antenna.

The hula hoop fits perfectly into the opening poked put of the box. Looks good.

Next step : Test transformer and 1M - 2G 32dB gain LNA.

Copper tape on small loop, with smaller box, and 1.5sqmm wire through the loop was tested. Not much space for transformer and amp in the box. Amp should just fit inside the box with connector, but not with connected connectors.

Using the copper tape for shielding is tricky to wind around the hula hoop, it gets uneven, and has to be done in short pieces with the simple "snail repellant" tape I am using.

I have an even smaller box. The smallest box only holds the 1M-2G amp if the SMA connectors are removed. This box should probably only be used with a soft wire/coax - (wire unshielded). Could probably be good with a loop circumference of 7.5 - 9m, usable up to about 10MHz.