Im looking for a antenna to use with my mobile 2m and 70cms radio . The idea is to have the radio in my bag or a small camera bag etc . Will a mobile colinear for a car work without a groundplane? If not if i fitted a so239 in a ali pole and strapped the side of my rucksack would this work .
What Andy said! But, then again, it depends on how you define “work”.
A hand held radio with a short “rubber duck” antenna is not a very efficient system, but it does “work”.
Either of your suggestions will receive signals, and radiate on transmit, but the performance will be a bit unpredictable depending on eg how long the coax is, what shape / angles it forms, how close the bits are to your body etc. A mobile radio is designed to have a nice 50 ohm load, so I would avoid running it into a strange antenna on full power, anyway.
You could use one of the “roll up” designs, fixed to a plastic pole, but I think you will find that any such antenna will whip around as you walk especially if you are covering rough ground…
You could have a mobile whip on a mag mount fitted to a wheel barrow which you push along…
Yes it is a mobile radio rather than a handheld , and i sort of guessed it would not work screwed directly in but my idea was if enough metal contacting the outside ground of the so239 surley this could work but depends on how much you need …instead of a wheel barrow enough roses tins would work !
a long flexible whip , what sort of whip ? a mobile whip ?
and yes the rig has a earth screw . i think the distance from the rig to the antenna would be more than 1/4 wave but i always been told you can not have too much groundplane .
Got any boots yet Matt? Get it spent and get outside… Weather forecast good for most of the UK this week… always good for Chasers any day, QSOs today with German, Mallorcan, Italian and Swiss summits. Trying for USA as I write this but cannot hear AA0BV so well I have to say…
The rucksack special mentioned above (some call it the flower pot aerial) works well for UK 2m FM contacts. Its an end fed half wave coax choked dipole and can be constructed from one piece of RG58, from the tip of the antenna down to the BNC or PL-259. Had 1000s of QSOs with mine in the rucksack completely tubed or mounted on a pole with the top half of the dipole taped to the mast. If you intend activating on the hoof I would forget trying to use a mobile radio. Suggest you get a basic handheld such as FT-270 or secondhand VX-170 and buy a speaker mic (cheapo from China - not essential you could just use the handheld as a walkie talkie) and use a home brew rucksack special or a rolled up open wire feeder wire slim jim fastened to a pole.
I’ve used my FT857D portable on 2 metres with a half-wave 2 metre whip and a right-angle adapter to the PL259 adapter to the N-type socket on the back - sounds terrible but it worked! For my FT817 I got from the late lamented Maplins a telescopic whip with a BNC plug end which was a quarter wave on 2 metres fully extended and a quarter wave on 70 cms fully retracted. I had intended to try it with a couple of counterpoise wires but tried it without and it worked so well I didn’t bother with any counterpoise. Its a good principle - try and see what you can get away with!
I also have made thousands of QSO’s on the flower pot aerial. Note that the coil is best configured as a self resonant coil (the inter-turn capacitance resonating with the coil inductance at 145MHz). The length/ diameter ratio is then important. I use one piece of RG174 for the feeder, coil and aerial.
The coil dimensions can be determined by constructing a coil without tails and then using a single turn coupling to an aerial analyser to determine the resonant frequency. In my case to top section of the radiator is 500mm long, the screened section 444mm, coil 8,5t 28mm long and 22mm dia… SWR about 1.15:1. Total cost including the kids fibre glass (not carbonfibre) fishing rod at Lidle, about £5.
Phil , yes i already have 2 pairs of boots fairly cheap ones but they do the job for the mo , went into go outdoors and the 3 boots i liked the look of had no stock in my size tried half size smaller but too tight with thicker socks on , so waiting for stock to turn back up . dont want to order a pair to find there not a good fit . Due to work i cant get out on any registered summits that are close to me for a hour or 2 trip out after work .
HF well i wont be operating on hf as my rig weighs 2.2kg so i think il leave that one at home or in the car ! with the bigger battery too . I have a 5/8 coaxial end fed 2m diploe i use now but i use on top of my 6m pole . So this is why a flower pot antenna is looking like a cracking idea . Oh the FT-270 is not sold now and only reason why wanted to use my mubile rig due to having more than 5w and its light and compact . 720g it weighs so not alot at all and upto 20w with a speaker mic too .
Matt, I’ve tried quite a few things pedestrian mobile for 2m/70cm, in all cases using a piece of PVC conduit to raise the antenna above my head, with various connectors mounted on top (started out with SO-239 and have also used N-Type and BNC where required):
dual band mobile/car antenna - nasty Nagoya works OK but isn’t flexible and catches on everything, and unreliable, cheap mobile antennas are to be avoided!
end-fed coaxial antenna - can be made quite flexible based on the housing you use, better performance on 2m than 70cm.
military 5/8 whip - this isn’t supposed to work without a ground plane but I found it performed better than the Diamond RH-770 which is my ‘go-to’ handheld antenna. These are designed for slightly higher frequency than the 2m band but the SWR response is quite flat. No good for 70cm however.
Diamond RH-770 - telescoping whip designed for mounting on top of a handheld - it is an exceptionally good antenna but you would have to be mindful of foliage as it wouldn’t take much to crumple it.
Here is a photo of me using the military whip with my FT-857 in a re-purposed camera chest harness. This was quite usable pedestrian mobile.
Good info from Mark M0NOM, who gets out well on 2m FM, You only get out what you put in…
OK Matt, Suggest then you buy a good secondhand 2m 5 watt handheld then or look for something equivalent and as good, new. Avoid the cheaper chinese radios and some of the wideband RX expensive Yaesu ones like the VX5R. The front ends become deaf when they get flattened by the commercial transmitters on some of the summits you may visit. More grunt from a mobile 2m FM radio is useful, depending where you are, sometimes I use a 20 year old 50 watt radio (Yaesu FT1500M), but other times when near connurbations with plenty of radio ham chasers then 5 watts and the RH770 whip is enough and you can travel light. Horses for courses. You must have the facility to self spot using an app or can rely on a friend to text to who is sat on a PC at home and who can spot for you.
Experience counts or look back through other activators logs and on the reflector to see what previous operators have used. It can be a gamble taking low power, lighter gear - you want to be sure you don’t set yourself up to fail by only getting two contacts from a summit which you have worked hard to get to because you judged your equipment needs wrongly, and then having to return another day when you could have bagged soemthing else. Time is another factor - how long do you want to spend on the summit before moving on to somewhere else. UK based SOTA HF operation usually takes longer than VHF. It takes longer to set up, you work more stations on HF which takes more time, but it is also more satisfying in my opinion. I tend to do both, it just depends where I am and who is likely to be in reach on 2m FM. As a chaser and an activator you get to know a lot of people over time and how they operate. That’s all part of the fun and interest of SOTA!
I had an FT-270 for a year or so and it is a very solid, dependable handheld. Like a brick. Obviously monoband, so you’re looking at 2m only, but unless you like accessing repeaters or are sold on 70cm then it is a compromise (just don’t let Viki @M6BWA hear me say that ) - chances are you’ll work the same folk on 70cm that you do on 2m, unless you get into SSB which is a different game entirely, and can be very addictive.
Take heed of @G4OBK Phil’s comments - they are based very much in reality compared to the idealized vision of SOTA that I had in my head when I started out. Horses for courses is right. For example the extra grunt of a compact, lightweight 20w-40w mobile transceiver definitely makes a difference over a handheld, but then you need to worry about batteries that can drive them at 13.8v (think LifePo4) and the extra inconvenience that entails.
On a beautiful, calm, sunny afternoon you could have a lot of fun, but on St Sunday Crag with a biting Easterly wind trust me an FT-270 with the standard whip or possibly pushing your luck, an RH-770 (you got to get your hands out of the gloves to put that on!) will be your friend.
Best of luck, it’s all about experimentation this hobby, do lots of it but be prepared to fail a lot too. Choose deliberately to be stubborn minded, ignore advice and go down your own route - you just might find something that works the best for you! Be prepared to refine things incrementally when you find something that works to make it something great. Also note that other folk have done that as well, there is lots to learn from those who have been before.
Oh, and I’ll just add, you can have handheld turned on all the way up and down to a summit, so will catch additional traffic over a rig that needs setting up.