Showing posts with label antenna. Show all posts
Showing posts with label antenna. Show all posts

11 Mar 2024

8m antenna repair

For reasons I do not understand my 8m dipole has gone to resonance at about 49MHz. It is simpler to replace the antenna and coax. Assuming the weather is OK, I may try doing this in the next week. 

At the moment I am inclined not to apply for an 8m TX permit again, but instead concentrate on ISM rules and WSPR. In the UK this means 10mW ERP and compliance with IR2030. In the UK this is totally free (no licence needed) and I believe open to all. As long as there are people monitoring, much of Europe should be within range on 8m WSPR in the Es season.

9 May 2023

V2000 vertical omni

On 6m, 2m (vertical) and 70cm (vertical) the V2000 is used. This photo was taken some years ago. On 6m with 1W CW the USA has been worked with this antenna. 

29 Apr 2023

Multiband antennas

Quite a good multi-band antenna is the end-fed via a 9:1 balun. At the end of the wire it presents a high impedance and the 9:1 balun drops the impedance to a low SWR, certainly less than 3:1 that can be tuned via the auto-ATU in many modern rigs. On many radios an ATU will not be needed at all. With QRP, RF on the coax is not usually an issue. With high power, more care or a counterpoise may be needed.

At the moment I am using an end-fed antenna. I have not found a counterpoise necessary.

Commercial versions are available (e.g. from Moonraker), although many make their own.

1 Apr 2023

Bicone antennas

Sometimes people want a wideband antenna covering several bands. One to consider is the bicone. these can be quite large, but can cover several bands.

See https://en.wikipedia.org/wiki/Biconical_antenna .

24 Sept 2022

23cm antennas (again)

At one time, a very popular 23cm antenna, for ATV I think, was the bow tie designed by G8GML (now SK). As I recall it was 2 diamond shaped elements with a solid reflector. I think it had a useful (not high) gain and a fairly broad forward lobe. 

For DX contacts, a decent beam with lots of forward gain is usually essential, but such an antenna might be better for me than the PCB HB9CV that, I believe, is supplied with the 23cm transverter that should come next month.

What I am wondering is does anyone make this commercially and at what price?

Such an antenna might be useful on 70cm too.

UPDATE 1907z:   As David says in the comments, Wimo make such an antenna. It looks expensive.

22 Sept 2022

23cm antennas?

As regular readers will know, I am buying a 23cm 2W transverter from SG-Labs in Bulgaria. I think at one time they supplied a small 23cm PCB antenna with it. I have to check if this is still the case.

Looking around, 23cm commercial antennas look very expensive. As the majority of QSOs would be local(ish), I am wondering what you would recommend? As my fine motor skills are not good these days, I don't think I could make one. In the past, I would have made one! Is there one that would be ideal for me?

19 Sept 2022

23cm antennas?

Next year, all being well, I hope to try some /P 23cm operation in some of the RSGB organised activity contests (UKAC). I am wondering if there is a popular antenna used in these contests?  

Clearly very high gain antennas will give good signals, but will miss stations that are out of the very sharp beamwidth, whereas smaller antennas will have broader beams, but less gain.  Perhaps, stations use one antenna for hunting, then a sharp, high gain one when on beam.

It is a very long time since I was on 23cm and then only RX.

Is there a favourite antenna?

17 Aug 2022

ICOM AH-5000 antenna


This antenna has just come to my attention. Like all things ICOM it is expensive. It is meant to cover all HF bands (maybe with a tuner on some frequencies). I have no idea how it performs. 

It looks like a Rybakov style antenna, but I have no idea. 

There are other, similar commercial antennas around which are far less expensive. 

11 Jun 2022

2m halfwave antennas


Most people opt for 5/8th wave antennas when they want better ranges on their 2m handhelds. Some years ago now I made a half-wave antenna for 2m. It was widely used on my many 2m rigs. It was first used in the 1970s, so must be about 50 years old! 

The idea was simple: the end is a high impedance so I just added a tuned circuit tapped at the 50  ohm point to match to the rig. It got me across the English Channel with a 10mW AM handheld (160km), so it must work! The antenna was actually on the Fredbox.

Clearly this would work on 70cm if scaled.

One photo shows the matching arrangement and the other the full whip.

23 Apr 2022

4 element Yagi for 70cms

Some years ago I was looking for an antenna for a 70cm contest to take out portable. It performed well with QRP SSB. Like similar antennas of mine, it was fabricated from an old metal coat hanger. It was a good match and used with my FT817. I still have this antenna in the back of the garage.

See https://sites.google.com/view/g3xbm4/home/antennas/70cm-4el-yagi .

30 Mar 2022

8m antenna erection

In the next 48 hours, I hope to erect a wire dipole for 8m. Years ago this would have been trivial, but I am not good on ladders since my stroke in 2013

Putting this up requires a minimum of 2 ladder climbs. Luckily, both are not very high, so I hope to manage these.

I am really looking forward to experimenting on 8m TX.

My floored loft has not been visited by me in 8 years!! There is quite a bit of amateur gear in one of the boxes.

UPDATE 1352z:  Small steps! As I get very tired these days I am doing this is small steps with rest in between. So far I have (1) cut the 8m dipole to length, (2) drilled the hole from the outside into the shack for the coax, (3) lowered the 10m antenna so I can attach the 8m dipole to it and (4) shortened the length of the nylon insulator that holds the 10m antenna in place. Now I need a rest!

24 Feb 2022

10m antennas

One of the beauties of 10m is antennas are small. A half wave dipole is only about 5m long. A halo is even smaller. 27MHz CB verticals can work very well too. 

Some years ago I wanted a simple antenna for the band and the Homebase-10 was born.

See https://sites.google.com/view/g3xbm4/home/antennas/homebase10-10m-halo.

16 Nov 2021

15m antenna?

Judging by the results on FT8 RX today with my very improvised 15m antenna, I am tempted to convert my Par end fed antenna to 15m. 

I suppose I could make it cover 10m and 15m by putting up 2 wires. Already today, I have spotted 350 stations on 15m FT8 RX. Don't forget that some of the time the PC had closed down with a flat battery too!  With a "proper" antenna , I would expect even better results.

All that should be needed to cover 15m is a longer wire.

1 Oct 2021

The most stupid product yet?

I have just received the latest newsletter from a major UK dealer. It included 2 products that seem pointless to me! For over £115 you can have a box that disconnects the antenna. For £190 you can automatically disconnect and ground 2 antennas.  Surely you can just unplug antennas? Am I missing something here?

Sorry, but this seems to be another way for the manufacturer and dealer to make money from gullible people or people with deep pockets. I for one will not be rushing...

6 Jul 2021

Homebrew 70cm antenna


This appeared as a FB memory today. It shows the antenna made from an old coat hanger for 70cm 8 years ago. The map shows the contacts with it. 

15 Jun 2021

Par EF-10/20/40

Last year, this developed a fault. 

I strung an end-fed wire using the Par transformer out of the shack window. The VSWR looked low, so I assume this Par transformer is fine. At some point I shall re-erect this tri-band antenna, but with new coax. Either there was moisture in the coax or the plug had failed.

In the past I have been spotted all over the planet with this antenna and 500mW WSPR on 10m. It is good for 35W, although my absolute maximum is 10W and often much lower. With WSPR and FT8 it is far lower.

10 Jun 2021

Fault finding my Par endfed 102040 antenna

Since taking it down I have realised I can check if the coax was faulty by connecting a 10m dipole (endfed at the shack) and running the wire down the garden. If it is the coax I can replace it and get on 10m, 20m and 40m.  

With this antenna I had 10m spots from all over the world (including Australia and Antarctica) with 500mW WSPR.

15 May 2021

V2000 vertical omni antenna faulty

This antenna must be very old now. I have had it for a very long time and it would not surprise me if it was 20 years old. 

Either it or the coax has failed as the VSWR has gone over 3:1. 

I may try a whip  (with counterpoise) on the rig to see how much worse this is. Repairing the V2000 is a major issue these days. 

21 Mar 2021

Moxon antennas

Someone today asked me if I still have my coat hanger Moxon for 70cms. Moxons (as the page shows) can be easily made and work well. I have not seen the antenna for many years, so I doubt I still have it.

See https://sites.google.com/site/g3xbmqrp3/antennas/70cm_moxon .

18 Mar 2021

10m dipole

One of the simplest antennas is the dipole made of wire. 

On 10m this is quite small being only about 5m long. Although I have been very impressed with my tiny indoor loops, an outside dipole should be several dBs better in the best directions.

Whereas, in the past, erecting this would have been a trivial task, my ladder days are largely over, so I depend on others now for erection. Hopefully my son can help in the coming weeks. 

It would be good to have this up before the Es season starts, late next month. By the autumn I think we can expect the USA to come through regularly on 10m, even on 10m AM just above 29MHz.

I have an idea on where to hang it. This should be good for North America and Europe.