PDA

View Full Version : Not a Ham yet but love radio.



YJunk
09-26-2012, 10:51 AM
Right now I'm happy being an 11 meter idiot and monitoring 10 meters. My passion is high gain mobile antenna systems. I've been actively designing and building multi-element mobile array's for nearly five years. I currently run a four element vertical array on the suburban when I'm shooting skip and have started designing a five element to replace it (refinement on the four continues though). I've also started work on a four element 10 meter design, should I ever get my license I can put that to good use. I'm tired of hearing all these international stations!

I did recently drag one of my licensed friends out to a mountain top to work the 2el 10m setup... I had a hard time getting him to leave LOL. Conditions were good and the antenna system was working well. We had zero issue working any station we heard - never got close to using the 200 watts the radio provides. Here is a shot of the original 2 element 11 meter setup. Vertical is noisy but it's nice to have a 5.3L "rotor" for re-positioning

46524

Spacing is 2/10wl. These sticks have now been replaced with straight aluminum - the large coil is pretty efficient but for stationary work it doesn't make sense to introduce any loss (if you don't have too - I get the multi-banded screw-driver antenna have their place. I'm just all about efficiency and max gain).

Plenty of counterpoise on the burb, the system tunes well (in mobile terms at least... accounting for ground losses, unbalanced system etc). The biggest issue right now is the phasing, I'll be having both the front and rear antenna mount modified to address that and reduce those losses. I've also got to pull the headliner again and improve the mount/body contact area - maximizing return current. It's a work in progress.

The rig is being setup to run legal limit (actually over-engineered in that area), it has a secondary red top battery in a recessed storage area to smooth out the current ripple (currently attached to the primary alt) and will provide power via a second alternator. I've chatted with Todd at Desert Fab about building a custom bracket to hold a 35lb Leece Neville 320. Just need to get around to it. Should run a big brick... That's a ways off though - I'm only just starting to scratch the surface of RF Circuit Design and can't even decide on a transistor much less properly design the combiner or biasing circuit.

The secondary alternator. She's a big girl for sure.

46525

I'll detail some of the work I've done here on the rig so far just for giggles - I've taken a lot of pictures along the way. More to come.

YJunk
09-26-2012, 11:25 AM
Continuing to work on the four element design.

I've been running the same spacing and lengths on the four element design for some time and recently got around to optimizing it. I started with the known parameters, the current spacing between the driven element and the reflector and my current total max boom length. From there I generated a bunch of random spacing in excel within certain parameters. Took each one of those and tuned it the best I could in EZNEC. From there I took the highest gain system and fine tuned it manually through the hunt and peck method. I've also been working on some additional optimization work that came out of some recent computer modeling over a massive test set... I'll spare you the details but this system is a "little" different than most yagi's or multi-element vertical arrays. Had a couple of friends (RF Enginners) in NY test it and it seems to work, so I'll take it to production and see if I can get it to tune in the field. Now if I just had a network analyzer :)

Theoretical gain of 7.83dBi over real ground. Unfortunately I don't have a good mesh for EZNEC yet and can't really account for the vehicle. Doesn't really matter though, this is just to get close, the real tuning and far field measurements are what matter. It's a pretty pattern though...

46526

azgypsy
09-26-2012, 04:35 PM
theres a couple hamm op's showin up on sat mornin at desertrat for the ryders run! could be an onteresting M&G for ya! dave

ShmUDE
09-26-2012, 04:39 PM
Continuing to work on the four element design.

I've been running the same spacing and lengths on the four element design for some time and recently got around to optimizing it. I started with the known parameters, the current spacing between the driven element and the reflector and my current total max boom length. From there I generated a bunch of random spacing in excel within certain parameters. Took each one of those and tuned it the best I could in EZNEC. From there I took the highest gain system and fine tuned it manually through the hunt and peck method. I've also been working on some additional optimization work that came out of some recent computer modeling over a massive test set... I'll spare you the details but this system is a "little" different than most yagi's or multi-element vertical arrays. Had a couple of friends (RF Enginners) in NY test it and it seems to work, so I'll take it to production and see if I can get it to tune in the field. Now if I just had a network analyzer :)

Theoretical gain of 7.83dBi over real ground. Unfortunately I don't have a good mesh for EZNEC yet and can't really account for the vehicle. Doesn't really matter though, this is just to get close, the real tuning and far field measurements are what matter. It's a pretty pattern though...

WOOOOSH! is the sound of that flying over my head.

YJunk
09-26-2012, 09:02 PM
I don't typically "mod" radios - I'll set mine up to run about 125% modulation with a 1kHz tone, which when I'm talking gives me about 80 to 90% modulation on average. Loud and punchy without being crunchy. This particular radio I did up as a comp radio with variable power. High power, high modulation, dirty splatter box that did it's job. Had a custom cover done for this one - thought the guy did a pretty good job.

46535

On this radio I also did a little something different with the variable power. The typical setup for the Uniden/Cobra chassis is to hard-wire the rf gain wide open and steal the pot for the variable. I like having the rf gain so I removed the standard squelch and grabbed a dual pot squelch/mic gain combo, removed the mic gain and replaced it with an rf gain pot from another radio... We called it the frankenpot. I eventually blew that radio up - they tend to run pretty hot - but stored frankenpot away for another day.

46536

YJunk
09-26-2012, 09:24 PM
I wanted a nice clean console mount for the radio. To do it I had to perform a couple of minor mods. The opening on this portion of the console was wide and tall enough to accomodate the radio but it had a taper that prevented it from sliding in more than a couple of inches. I cut the back of the insert off but...

46537

... as you can see when it was all installed there was still some clearance issues.

46538

Pulled the seats and center console and modified the back of it to allow the coax and connector to clear the back of the console. It's still a tight fit and I'd like it back a little further, but it works.

46539

Allen
09-26-2012, 11:37 PM
I like radios too!




.....and bacon!

YJunk
09-27-2012, 07:30 AM
I like radios too!




.....and bacon!

I have some cheese waffles in my pocket, will that do?

YJunk
09-27-2012, 08:05 AM
The next step was to improve the power supply. I bought a large case CS144 to replace the standard small case alternator on the 5.3L, installed it and then ran it around phoenix for a about an hour. Once it was good and hot we pulled the alt and threw it on a carbon pile and tested it under load. Advertised as a 200 amp alt it would barely hold 130 amps when hot (this is pretty much the norm, Alt advertising is full of smoke and mirror bs). Custom hand wound stator, better rectifier and regulator and the unit will hold 140-150 amps at 14v on a carbon pile when hot. That's fine for now. Eventually the Leece 320 will be sitting next to it and the load on the primary alt will be a lot less.

From there I prepared for the rear battery bank. Ran 1/0 gauge welding wire under the truck and up through the floor underneath the rear seats.
Initially the rear battery bank consisted of four redtop batteries held in place by 2 of 4 Wheeler Supply's Dual Battery boxes. These things are beef.

Here is half of the original bank.

46543

It's probably worth noting that I've abandoned this rear bank design. After a lot of testing it was determined it was less load on the alternator to simply provide the required power to rear of the truck and not have to also try to charge four batteries at once. Now a single red top sits in a storage area out of site just to smooth out the ripple.

YJunk
09-27-2012, 08:15 AM
Once that was done it was on to the antenna mounts.

The antenna system is heavy and many of the drive around designs also add a lot of wind load stress to the mount area. So it requires a large mount. The most typical setup is a puck style mount and that's what I used. This design required two pucks to be installed 86 inches apart, one in the rear and one up front. That meant dropping the headliners. To accomplish that, both over head consoles had to be removed, all pillar trim came out, rear ac duct work was removed and the gauge cluster was removed to access the connection point for the over-head wiring harness. Good times.

http://i1051.photobucket.com/albums/s422/finran/dash.jpg
Gauge pod removed

http://i1051.photobucket.com/albums/s422/finran/headlinerDown.jpg
Headliner down (finally)

The hardest part of all of this is keeping the thing clean. Once these things get dirty it's really hard to clean them without damaging them.

YJunk
09-27-2012, 09:17 AM
The rear puck was pretty straight forward, the picture is pretty self explanatory. The only this that is different at this point is how the rear puck is grounded to the body. I've ditched the wire for braided strap which flows rf a little more efficiently.

http://i1051.photobucket.com/albums/s422/finran/rearPuckInside.jpg
Rear puck inside

http://i1051.photobucket.com/albums/s422/finran/finishedPuck.jpg
Rear puck outside.

YJunk
09-27-2012, 09:28 AM
The front puck install was a little more involved. On the 2003 Burb's the overhead console has it's own mounting framework. This had to be opened up to allow the installation of the backing plate.

http://i1051.photobucket.com/albums/s422/finran/overHeadConsoleBefore.jpg
Before

http://i1051.photobucket.com/albums/s422/finran/frontPuckInside.jpg
After

Once the front puck was installed I ran a half-wave length of 213 coax up inside the B Pillar, out through some heater hose and into the puck. It's zip tied every six inches or so to prevent slapping over bumpy roads.

http://i1051.photobucket.com/albums/s422/finran/overHeadWithCoax.jpg

After that the mobile antenna test bed was pretty well finished. The only non-antenna project left is the watt meter. I have a single line Bird section to measure forward or reflected power. I spent two years looking for a meter movement that didn't have a white face and finally found this. The bezel and "glass" were in pretty rough condition when it showed up. The glass turned out to be a thick plastic of some sort and I was able to clean up all the scratches and damage after about a days worth of polishing. Shot the bezel some new black and we're good to go. This will occupy one of the cup holder when I get off my rear and address it. As of right now I've been more interested in the antenna design side of things...

http://i1051.photobucket.com/albums/s422/finran/birdMeter.jpg