Auto antenna tuner with a mobile export?

[btu44]

Hello again,

Another question since you guys are so helpful.
I'm thinking about installing a MFJ 925 auto tuner in my mobile rig. It's just that money is so limited that I want to be sure it is a good idea.
Here some pictures of the current antenna setup I have.

This is the Procomm antenna for off roading with a group. For some reason spotters don't like getting hit in the face by a SS whip antenna

I use this whip antenna in the desert for best performance and a wider band width. It's disadvantage is it's 13' 10" high and is a hell of a tree wacker.

The mast is drilled almost through so I can tune from the bottom of 11 meters to the top of 10 meters.

This is the manual tuning kit for setting up the whip antenna. With the antenna at maximum height, it covers 11 meters. The short black zip tie tunes from 27.005 - 28.5Mhz with an SWR under 1.7:1. The white zip tie covers 28.3 - 28.5Mhz with a SWR of not over 1.2:1. The long black zip tie covers 28.3 - 29.7Mhz with a SWR under 1.5:1.

So I'm thinking the MFJ auto tuner would be cool because it has the audible SWR warning in case the antenna is in the wrong adjustment. I like that the tuner has 2 memory banks, one for the whip and the other for the 5' Procomm.

Do you guys think the auto tuner would work well with this setup? Do auto tuners improve receive on non resonant antennas? While driving with the Procomm, the antenna moves around a lot on the spring. Because of the large amount of parallel metal of the cab of the truck the SWR varies quite a bit. Would this freak out the auto tuner?

 

[wavrider]

How much power you using ( watts?).

A simple manual antenna tuner in the 300 watt range is less expensive than an auto tuner and is small enough to be portable.

Or use an LDG type tuner if you want semi auto tune push button type

 

[M0GVZ]

Look at the SGC237 or SGC230. You would be able to tune that whip from all bands from 80m to 10m.

 

[btu44]

How much power you using ( watts?).

A simple manual antenna tuner in the 300 watt range is less expensive than an auto tuner and is small enough to be portable.

Or use an LDG type tuner if you want semi auto tune push button type

I'm running 150 watts on SSB and up to 50 watts on FM.

I would like to run a manual tuner but there is very little available dash space in my truck. I have just enough space for the ICOM IC2730A I've been eyeballing for awhile.

I've looked at the LDG AT-200ProII and seems to be of better quality than the MFJ unit but it's too high to fit under the seat. LDG said it was possible to repackage the electronics but there goes the warranty.

Another route I was thinking of was making this SWR meter:
http://www.qrp4u.de/docs/en/swr_meter/

Problem is I don't have the knowledge to scale it up to my power levels. And I wouldn't be surprised after buying parts, packaging and time, I'd be getting close to the price of an auto tuner. But I maybe wrong???

 

[btu44]

Look at the SGC237 or SGC230. You would be able to tune that whip from all bands from 80m to 10m.

I appreciate the suggestion and that is a real nice tuner. It looks perfect for mounting under the seat but it may not take the power and it's outside my budget.
Thanks anyways.

 

[M0GVZ]

I appreciate the suggestion and that is a real nice tuner. It looks perfect for mounting under the seat but it may not take the power and it's outside my budget.
Thanks anyways.

It does 100W, how much more do you want?

 

[wavrider]

http://www.worldwidedx.com/threads/...antenna-tuner-mobile-base-camping-ect.188254/

Not an auto tuner but the price is right for most budgets

 

[btu44]

http://www.worldwidedx.com/threads/...antenna-tuner-mobile-base-camping-ect.188254/

Not an auto tuner but the price is right for most budgets

That's a great price but it's too big to fit in my dash area to be operated. Plus I would need to find room for SWR meter.

I called SGC and they said the SG-237 could hand 50 watts FM but some component would get pretty hot after a half hour of transmit. Not a problem there but at $300 I'd rather put towards a 2m/70cm radio.

 

[fourstringburn]

Do auto tuners improve receive on non resonant antennas?

One thing no one has mentioned yet.

An antenna tuner doesn't tune an antenna, it just matches the radio to a mismatched load usually caused by using an antenna outside of it's resonant frequency range. The antenna tuners purpose is so the radio can operate safely within this range that the tuner tuned.

So to answer the question about receiver improvement, No, because your antenna still hasn't changed any physical or electrical length by using a tuner, Your antenna still stays the same.

You have a manually tune antenna that can be adjusted at the antenna itself for different frequencies or bands. This is truly tuning the antenna and will improve performance on each band compared to using a antenna tuner with a antenna out of resonance.

Generally Amateur radio operators use tuners when using multi-band antennas like certain types of dipoles and others since these may closely resonate on some bands but not on others. This let's the operator use 1 antenna for multiple bands and at least maintain a low SWR for the radio and amplifier if one is used. Yet, the antenna will still have a high SWR after the antenna tuner on some bands but this is the trade off for using a multi band antenna as opposed to using several mono band antennas cut to length for a given band.

I would suggest using a good mobile SWR meter over buying a tuner and manually tune your antenna to switch bands if you want the best performance on each band. If your SWR readings are fairly accurate as you mentioned, you are good to go on 11 and 10 meters already. Don't get too hung up on SWR readings until you start getting over 1.8:1.

If you want something in a automatic tuning multi-band mobile antenna, then look into using a screwdriver antenna where you can have a sophisticated setup only limited buy your needs and finances.

 

[fourstringburn]

While driving with the Procomm, the antenna moves around a lot on the spring.

If that Procomm antenna is only 5ft or so, You shouldn't need the spring. Have you tried it without?

 

[Captain Kilowatt]

One thing no one has mentioned yet.

So to answer the question about receiver improvement, No, because your antenna still hasn't changed any physical or electrical length by using a tuner, Your antenna still stays the same.

Actually an antenna tuner can abd does help the receive end in a lot of cases. If the antenna is quite short or the match is WAAAAY off it allows a more efficient coupling to the receiver and the signals do improve. Many times I have had a pretty deaf receiver and after hitting the TUNE switch on the auto tuner the receiver jumps to life. I have seen this with an 8 foot antenna while mobile on 20m and down as well as on my 80m ladderline fed doublet on any band that the tuner is not set for. If the SWR is already something like 2:1 however the difference is hardly noticeable if at all.

 

[w9cll]

One thing that nobody mention is the op is planning to use this setup off road, I highly doubt the mfj tuner will survive under those conditions. They are made too skt comfortably on a desk.

 

[fourstringburn]

Actually an antenna tuner can abd does help the receive end in a lot of cases. If the antenna is quite short or the match is WAAAAY off it allows a more efficient coupling to the receiver and the signals do improve. Many times I have had a pretty deaf receiver and after hitting the TUNE switch on the auto tuner the receiver jumps to life. I have seen this with an 8 foot antenna while mobile on 20m and down as well as on my 80m ladderline fed doublet on any band that the tuner is not set for. If the SWR is already something like 2:1 however the difference is hardly noticeable if at all.

What happens here on your 80m doublet is your auto tuner is out of band sort of speak until you hit the auto tune button. This happens every time I power up my radio and auto tuner or change bands until the auto tuner is activated with my Windom antenna. After I hit the auto tuner, then the band comes alive. This doesn't happen with a manual tuner at least when turning on the radio on the last band used with the tuner.

As I said before and I know you know this, the antenna tuner doesn't change your antenna's physical or electrical length with the tuner, your antenna remains unchanged just as before.

After re-thinking what I said earlier, on short mobile antennas, adding a tuner is similar to a screwdriver antenna which is basically a shortened antenna that some can cover even 160m ( with little efficiency) by adding inductance in the form of a loading coil. Most tuners add both inductance and capacitance to match the antenna load. To effectively match a shortened mobile whip antenna on multiple bands the tuner should be placed at the antenna feed point with a lead connector as short as possible. This is how the Icom AH-4 tuner /whip combo is used and how any whip/combo should be used. A desktop auto tuner wouldn't be practical in this case.

In the OP's case, his antenna is already within range of the bands he operates in so using a tuner wouldn't make a noticeable difference on receive or transmit just as you said even with a 2.1 SWR.

I would then still stand by suggestions about using a good SWR meter and manually tuning his tunable whip antenna or consider a screwdriver antenna in the future. If a tuner /whip combo is still preferred, then a outdoor remote tuner must be used and properly installed as mentioned previously but the expense would probably be the same as a screwdriver antenna like the Little Tarheel series screwdriver antennas.

IMHO, The Palstar PM2000am is the best choice for a mobile SWR meter since it has remote coax connectors so the coax doesn't have to be routed to the meter and the meter can be installed anywhere the operator wants and only a single sensor wire has to be run to it.

 

[The War Wagon]

This is the Procomm antenna for off roading with a group. For some reason spotters don't like getting hit in the face by a SS whip antenna

A gutter tie-down is no guarantee that WON'T happen, but it doesn't hurt.
Here's the one on my RC in my avatar.

But I notice newer trucks like yours, no longer have gutters!!!

 

[Captain Kilowatt]

What happens here on your 80m doublet is your auto tuner is out of band sort of speak until you hit the auto tune button. This happens every time I power up my radio and auto tuner or change bands until the auto tuner is activated with my Windom antenna. After I hit the auto tuner, then the band comes alive. This doesn't happen with a manual tuner at least when turning on the radio on the last band used with the tuner.

As I said before and I know you know this, the antenna tuner doesn't change your antenna's physical or electrical length with the tuner, your antenna remains unchanged just as before.

After re-thinking what I said earlier, on short mobile antennas, adding a tuner is similar to a screwdriver antenna which is basically a shortened antenna that some can cover even 160m ( with little efficiency) by adding inductance in the form of a loading coil. Most tuners add both inductance and capacitance to match the antenna load. To effectively match a shortened mobile whip antenna on multiple bands the tuner should be placed at the antenna feed point with a lead connector as short as possible. This is how the Icom AH-4 tuner /whip combo is used and how any whip/combo should be used. A desktop auto tuner wouldn't be practical in this case.

In the OP's case, his antenna is already within range of the bands he operates in so using a tuner wouldn't make a noticeable difference on receive or transmit just as you said even with a 2.1 SWR.

I would then still stand by suggestions about using a good SWR meter and manually tuning his tunable whip antenna or consider a screwdriver antenna in the future. If a tuner /whip combo is still preferred, then a outdoor remote tuner must be used and properly installed as mentioned previously but the expense would probably be the same as a screwdriver antenna like the Little Tarheel series screwdriver antennas.

IMHO, The Palstar PM2000am is the best choice for a mobile SWR meter since it has remote coax connectors so the coax doesn't have to be routed to the meter and the meter can be installed anywhere the operator wants and only a single sensor wire has to be run to it.

We are talking the same language on this. My auto tuner is a Yaesu FC-40 that I used mobile with about six inches of heavy conductor to the antenna. It is (was until a few days ago) remote mounted outside the house between my coax feedline and the 450 ohm ladderline to the antenna. I know what you mean about the tuner being off resonance and should have mentioned that however there are times when a tuner will add a couple S-units to receive simply switching from bypass to the tuned position depending on the frequency and impedance of the antenna. I have seen this with my manual tuner and again, it is more noticeable on the low bands with a short antenna.