New mobile antenna

[northern35s]

Ok, so my thing is mobile radio, be that on foot, bicycle, or in the car, usually by the sea, however I spend a lot of time driving to and from work so that forms the bulk of my on air time.
When I park up for a DX session, I like big antennas, 1/4WL antennas to be precise, now this isn't such a problem for 10 or 12m, but a 1/4WL soon grows in size when one starts to go lower in frequency. I had been thinking about making a multiband 1/4WL antenna, manually adjustable, that would attach to my car, there were a couple of requirements that the antenna had to fulfil.

1) sturdy, we get a lot of wind by the sea and I've had a fibreglass antenna snap previously

2) Multiband of course

3) Work on my favourite DX band, 20m

4) Roof height, no obstruction or opposing currents from the car

5) Easy to deploy

Well the best I could come up with is a converted CB 1/2WL antenna, the Silver Rod, as it is known in the UK, seemed to fit the bill, alloy construction, comes with mounting flange and fittings, easy to modify, easy to tune, and sturdy, here's how it's working out, from modification to deployment:


The impedance transformer in the base of the antenna

The coil attached to the SO239 socket

The removed coil, apparently capable of handling 1000W

Coil bypass wire in place of the coil

Coil bypass wire soldered to the SO239 and ready to close up

In the transit position ready for driving

Antenna in use, a trailer hitch and short stub mast below the antenna

I haven't finished yet, I've got to install some ground straps from the base of the antenna to the door frame of the hatchback, run a choked coax through to the transceiver and fine tune and mark the antenna up for the different band positions.
As a quick test I ran a long coax lead through to the rig, the length accounting for the missing ground and relying on CMC to make up the other half of the antenna. I tuned through 20m and found a friend of mine was out locally pedestrian mobile, he was working a VE7 so I joined in, but due to a high noise level I couldn't hear the VE7, however he could hear me better long path than short path, which is no surprise as my house was blocking me to the North. The second station that called in was on the Island of Mauritius, a rare DX entity on any band, both my friend and I were around 58 with him and he 59 with me, I didn't stick around any longer, I had to get my gear packed away as I had other things to do, but I was very happy with my first contacts on the new antenna.

For info the antenna cost around £25, the tow hitch assembly £75, this is just the first of many antenna projects for the car, looking forward to some warmer weather before I build the rest


Edit: just realised I put this in the CB section, I don't mind it being here if you guys don't :blushing:

 

[W5LZ]

I like doing HF mobile too. I did it the easier way, just use a 'loaded' antenna. It's a 1/4 wave on 10M, but not on the lower bands. That deals with not having to un-assemble things when I move, and using bands lower than 10 when in motion.
Used a 'Texas BugCatcher' for a lot of years, it's a PITA to set up correctly to start with, finding all those coil taps for each band. But, once you do find them, it's just a matter of changing them to change bands. The last couple/few years I'v gotten lazy(er) and switched to a screwdriver antenna. Works just as well, but I don't have to stop to make those coil-tap changes.
There's a big difference in our operating 'styles'! You are sitting still so you have the option of using a 'real-live' 1/4 wave on all bands. I'd rather sit at work, or do that operating while moving. We've both the same 'handicaps' for those lower bands (unless you string out radials?). Your method probably does mean a few more contacts, but I'd be willing to bet that the difference isn't gigantic.
Guess it's just different 'strokes' for different folks... Who cares, have fun.

- 'Doc

 

[northern35s]

The screwdriver is my day to day antenna and my home brew bugcatcher style 8' antennas are my preferred choice for DX, for 40m and 80m I use the screwdriver antenna with 5' element and huge capacitance hat, if I'm really going for it then I use a full size 1/4WL for 40m and an inductively and capacitance loaded 30' antenna for 80m, yep a few antennas in use here.

A friend of mine uses a pair of phased 1/4WL antennas for 40m and a 1/4WL for 80m when operating by the sea, he also has a 12m tower attached to the back of his van for his homebrew 4 element 20m yagi, he does big

 

[W5LZ]

The only thing I've ever done remotely like that was setting up at a lake near here. But I cheated when I did. The Corp of Engineers built 'facilities' on the lake shore, restrooms, picnic tables etc, and I found one such place where I could get a dipole into the trees and run an extension cord to one of the 'bath houses' for AC power! I was doing a WAS on 80 meters and had to do something different than at home. Amazing difference in noise levels between the lake are and my home in town. Also surprising, it wasn't Alaska or Hawaii that was the hard one, but Maryland. Once while I was there I happened to have a spool of wire and extended that 80 meter dipole for 160 meters. I got it as high as possible but most of it was laying on bushes maybe 4 feet off the ground. Made a contact or two on it too! Ah, them were the days, right? Oh well... Not exactly a mobile antenna, but I did operate from the car!
- 'Doc

 

[K9GAS]

I finally ran into a guy that actually runs the scorpion with the 160 coil and that thing does really well! A nice lazy way to work all the bands with a switchable coil, BUT expensive. Very impressive and not too tall compared to a 160 bug catcher and according works pretty close to it.

 

[northern35s]

There was a chap locally selling his as new SA680, I was soooo tempted, but had to think, another antenna or an AIM4170C antenna analyser, with the former I'd have a good mobile antenna, with the latter I'd have a very handy tool that would help me build as many antennas as I fancy, a bit like give a man a fish and feed him for a day, teach him how to build antennas and he'll happily go hungry until he's finished building just one more

 

[W5LZ]

A SA680 or your analyzer. I'm glad it was your decision and not mine! I'd have a lot of trouble making it. I have the '680-Shorty', but can't use it on my present vehicle. Almost wish I'd have gotten the analyzer... but not quite, I've got another brand.
- 'Doc

 

[K9GAS]

I've already have analyzer, I'd be happy to possibly take that SA680 off his hands.

 

[W5LZ]

Hmm. I'd make you a really good deal on that 'shorty', with or without the car. Only about $20,000 difference...
- 'Doc

...hold my breath, right?

 

[K9GAS]

Yeah, hold the mayo, huh car.

 

[northern35s]

I know I should have stolen the money out of my wife's purse and buy both, I regret not buying it as the Scorpion was selling for £390, and if I was to import new to the UK it would cost around £1,100, but my head ruled the heart this time.
I already have an MFJ269, but I've promised myself an AIM4170C for a long time so held firm and saved my cash, maybe next time :sad:

 

[W5LZ]

...stolen the money out of... Ooooo, you're a braver man than me to even say that within hearing distance of any female (much less your wife)! They pass that sort of information around you know? Not sure about the 'modern' generation of women, haven't seen many of them with a purse at all. I can say from experience that with the generation my wife was a part of, if you even touched a purse you were in trouble!

I can also say that the shipping packaging of any of the Scorpion antennas is definitely a selling point. If you haven't experienced that, you are definitely in for a surprise. There are un-packing instructions and you DO have to follow them. Otherwise, you are -not- going to get the thing out of the shipping 'tube'! Naturally, I didn't follow those instructions, to start with, and had to start over.
I very seldom ever can't find some 'fault' with something. That antenna is one of those exceptions, it's as close to 'perfect' as anyone can make one.
Okay, end of 'commercial'. If you haven't had direct experience with one you are so 'deprived'!
- 'Doc

 

[ghutch]

I like the bumper mount! I have a receiver hitch and have thought about using a extension to get the mast about 3 feet behind the truck bed.....using the "U" bolt the mast can be lowered all the way to wet sand and give a little more strength.

 

[Line]

I know this thread is over a year old but I was wondering how well it worked out, and if you ever got around to adding a downward radial system made from just wire, maybe with alligator clips to the antenna base (and a brick or ground stake for each lower end?) to give you quick assembly once parked?

 

[M0GVZ]

This is his Youtube channel. It both annoys me and motivates me listening to him occassionally on 20m as conditions allow talking to Australia from Blackpool seafront pedestrian mobile. Once heard him talking to VK using 500mW.

Stephen Salmon - YouTube