Just wondered if anyone knows anything about the Diamond RHM-12 mobile antenna?
Reason I tagged it ‘elusive’ is because nobody seems to have written a single word about it, so I haven’t a breeze if it’s worth trading a medieval coin purse of Florins and Guineas for.
There’s a couple of videos on YouTube but they are in Japanese. No trace or mention of it from the usual sponsored shills.
If anyone thinks it might be good to have on the motor, strapped to a triple magmount and a Diamond MAT-50, hooked up to an FT-891 (with optional MAT-30 ATU if it helps), I’d love to get some thoughts on that before bankrupting myself.
Side note, I considered an ATAS, but there’s a lot of arguing about 40m not working and strapping it to the car with more bonding than a Just Stop Oil protesters hand and a painting of Sunflowers.
Arguing belongs on 80m, between gatekeepers, and about gout and who has the most ailments.
Thanks in advance for any opinions.
73!
Edit: First article I’ve found, from a blogger in Japan.
I bought my Komunica when in Seville from Sonicolor es
I also got the tripod mount adapter for it
With proper radials it does work good for portable operations but you have to use raised radials to get the match right. Their length has to be adjusted as well as we try to mimic a car body
This antenna is sold (or copied) under quite a few brand names, but they all appear to be very similar. Stephan @HB9EAJ did a video on how he adapted it for ground mounting for space restricted summits:
Don’t expect great perfomance below 20m, and as Stephan says you can safely leave the 80m coil at home!
I built a version similar to Stephan’s setup as my stealth antenna for locations (POTA/SOTA) where I can’t get away with putting up a more noticeable antenna. It works fine on the higher bands for this (better than no antenna in these circumstances!).
I know 10m is great at the moment, but I did a local POTA the other day using this setup on 10m and worked reasonably far across the US and also down Chile with 5w using CW. I won’t have much expectations on the low bands however.
Hi Ian,
As others have said, the Diamond RHM-8B and 12 are antennas imported and sold by Diamond for many years. They consist of a slidable coil section on the bottom that is effectively the ATU. The RHM-8B has a BNC plug and was targeted at the FT-817/817ND market. I’ve never seen the RHM-12, but could it have been a similar antenna only with a PL259 connector?
As others have also said - the Spanish “Komunica Power” company design and sell a range of antennas both directly and via their distributors.
The HF-PRO-2-PLUS-T is a brilliant antenna when used either roof mounted on a magnetic base or used portably on a tripod with radial wires (also available from Komunica Power - or make your own tripod - an old photo tripod can be converted).
The HF-PRO-2-Plus-T came out about 6-7 years ago from which time I have had one and it ALWAYS performs! Unfortunately, 2 years ago, some Chinese company decided to copy the design and sell it at half the price through MFJ and some other US dealers, and I believe some UK importers. The Chinese copy appeared at Friedrichshafen in 2023 and a colleague of mine bought one. Being a copy, it works just as well as the original, except it comes without the 80m additional coil- so it is really a 40m - 6m antenna. I prefer to buy from the European company who designed it but that is always it’s buyers choice, whether to support a “local” company or buy cheaper from another company who stole the design.
You don’t need an ATU with the HF-PRO-2-PLUS-T - it, like the Diamond RHM series has a slidable bottom section that is your antenna matching.
Dont be tempted by the antennas that have a coil at the bottom and banana plug leads to short different parts out. If you can get those to work, they are a bad alternative to the HF-PRO-2-Plus-T. By the way, there is also the HF-PRO-2 which is the same antenna but with a solid rod element rather than the telescopic one. It works just as well but needs more space if you take it with you travelling.
Thanks for the invaluable advice folks! Just picked up that Komunica from Barcelona there for €78 plus postage. Hopefully it’s genuine.
Just need to source a triple mag mount and a Diamond MAT-50 now.
That Komunica looks very adaptable. When the weather gets better next year I might take it further than the vehicle roof.
Not too fussed about 80m as I’m not a radio gatekeeper and I don’t have gout.
I do have a Chameleon LEFS 8010 though so can always slope it off a tree or a 10m mast (if i can reverse it with the feed point at the bottom, else I’ll scrap the mast and chuck the thing up a tree if I want to have an argument on 80m.
I’m almost ready to sit my HAREC Class 1 CW upgrade exam, so hopefully will make my first ever CW QSO before 2024 is over!
Hi Ian,
Komunica also sell the triple mag mount, but if you will only be using the antenna when parked-up, a single magnet one is fine. This antenna is not suitable for use when the car is in motion in any case.
Also if using the HF-PRO-2 (with or without the Plus-T) (if that’s the one you ordered) you do not need an auto ATU as you must set the bottom coil by sliding it for maximum receive noise and if that is not in the right place an AATU is not going to help you.
So by going for this antenna, you have saved the cost of the ATU (unless you want that for a long wire antenna or whatever).
73 Ed.
PS - I’ve just checked - the eBay link you show is for one of the Chinese copies. As I said - half the price. The one my colleague bought came with no instructions or calibration chart, so I lent him my documentation from the Komunica Pro-2 and that was very close (this can be downloaded from the web).
I had a look there but can’t seem to buy the Komunica mount online. Long Communications in Ireland sell a similar one for €65 so will probably go with that and support the only han shop in the country.
I won’t use my MAT-30 (atu) but I reckon a Diamond MAT-50 grounding mat might be worth it?
I use my ATU with my JPC PAC-12 and it works brilliantly. Just now it’s approaching Winter, I’ll sit in my car in the warm rather than sit outside getting piles and pneumonia on a park bench in a downpour!
I’ve saved a packet buying the Komunica over the Diamond. Might put that towards a smaller QRP radio in the New Year to go with my 891. A little Xiegu 6100 or something second hand.
Also have a QRP Labs QMX on the way, I’m in the waiting list to have mine shipped, so 2025 will hopefully be a big year for me on CW.
Excited for the year ahead now, always something to learn and do in the radio community, great fun!
Edit: Random thought there on the Komunica. Can I connect my FT65DE to it for 2m and 70cm via the mag mount and an adapter?
Sorry mixed the two "mAT"s up. Grounding mat - here’s a simpler idea that works - buy a single magnet mag mount from your local Irish dealer and then buy a piece of Faraday cloth off the web.
To use the antenna away from the car roof, take the antenna with the mag mount and sit it on the Faraday cloth on the ground. It works, I have tried it. It’s not as good as using a tripod with radials, but it is far simpler and quicker to set-up.
With the adjustable coil pushed right down, you can then adjust the whip section down to be a loaded 1/4 wave on 2m or 5/8 on 70 cm. I’ve had it on the antenna analyser to prove this. This will not however perform as well as a “real” 1/4 or 5/8 wave whip and should only be considered when you don’t have those whips with you.
73 Ed.
Going by the copy my colleague bought (and is still using 2 years later) - it’s not junk - just not the original, designed by Komunica Power in Spain and built in Taiwan. The Gabil/Sharman/MFJ are unauthorised Chinese copies.
+1 for this. Just received 3m x 1m of Faraday cloth last week and amazed that all my mobile whips right down to 80m are happy sitting on it (same VSWR as on the fixed mount on the ute).
Was very sceptical - especially as the main target audience for the product seems to be to allow them to make more comfortable tin foil hats. But the stuff seems to be a very effective groundplane
I have the RHM-12, I purchased in Japan Oct 23. I also had the Kommunica one, which I believe is made by Gabil antenna and like others mention sold under different names. I purchased under the sharman md-3500 name from Moonraker.
I use/used both portable. The Kommunica has been a superb antenna, I have worked dx with SOTA and it’s great for a small impact quick deploy antenna.
Bottom line: Both do the same thing electrically, the Diamond is slightly bulkier but finished to a much higher quality. With a telescopic whip you stick need to take care to avoid damaging.
Unless like me you are lucky enough to be in Japan, the price of the RHM12 is not really worth with it. I can recommend the Kommunica/Gabil/Sharman.
Brilliant to read from someone that has actually used the mysterious RHM-12! Not just that, but with the Diamond and the Komunica!
I agree, if they perform essentially the same, then the huge price leap just isn’t worth it for slightly better build quality - I have a couple of Diamond antennas for my HT and Uniden and they really are lovely build quality and perform well.
I found a store in .nl that sells Komunica stuff at a reasonable price. Does anyone know if its genuine Komunica products and not copies?
I’ve cancelled the eBay order. If the cancellation goes through (can’t see why not?) I’ll get a legit Komunica setup.
That Diamond build quality though, I guess that’s where the premium goes is it?
As forKomunica, it’s not British Leyland build quality is it?
