Will the best AM/FM antenna please stand up?

[Doug Hicks]

I installed a Jensen JHD910 on my commuter St1100 with a 'powered' antenna. Can't pick up any AM and the FM reception is limited. What's available that is too small to support a fox tail or anything else you see on a typical land yacht? After all, my bike does have ST in it's name.

 

[st1300r]

powered antenna as in it retracts when the radio is off? or amplified?

where's it mounted, it's probably expecting a ground plane (mounted on a metal surface)

 

[ST1100Y]

Methinks an amplified (but having motor antennas in the panniers would indeed look kinda cool ;-) )
Aerials are always bit of a trouble on a motorcycle, designed to work against a metal car body they suddenly find themself slightly lost on all the Tupperware of a motorcycle ;-)
Adding an additional ground wire from its base to the frame might already make some improvement.
Or mounting it on a metal beam bolted across the carrier stay, providing good conductivity to the frame plus keeping the aerial exposed and errected.
But it could also be that the aerial or its cable is simply defective, like the core having a short towards the screening/mesh/ground somewhere in a crimp/plug/connector.
For trial and error I'd give it a try with a different antenna.

 

[Doug Hicks]

The 'power' is to amplify. The coax is quite long and the antenna itself is a plastic rectangle box . The directions said the antenna could be laid on the dash or glued to the windshield.

 

[ST1100Y]

The directions said the antenna could be laid on the dash or glued to the windshield.

Ah, that kinda thingie...
Frankly spoken, I'd forget about it... even in a car they barely work...
As far as I understand the technology, must an aerial (in real nothing then a conductive rod) have a specific length, matching the frequencies its supposed to operate on.
The short rubber/flex antennas for cars, meeting a compromize to that by having the specific length coiled up inside.
So if you want a hidden aerial, to prevent tempting and vandalism, I'd pick up such a rubberized thing from the nearest auto-store and hide it topside within the cowl/fairing, like above the headlight, and again install an additional good ground wire from its base to the frame to improve reception.

I have a 45cm/18" BOSCH AutoFlex antenna sitting on the rear top corner of the LHS pannier base since many years now.
It nicely shows the calibrated length of cable wound around its outside (the whole fibreglass rod is shrink wrapped)
It came with the little amp, tried it with and without the 12V lead connected, that amp thing does nothing truly noticeable at all (and thats an expensive brand antenna).
The reception is bearable, but not realy stunning, it simply misses a large steel plate as base wo work against; they however work brilliantly installed on a car, top notch.

Many years ago I'd modifyed a top box lid with an aluminum sheet inside, a think ground lead to the frame and an aerial on top of the lid; now that worked rather good,
but again only in the plains, cause once you vanish into the deep mountain valleys, or take a turn between the high risers in a city, the reception suffers again, unless you'vea
real strong local station tuned.
So I run my very own program from the iPod plugged into the changer interface of my Sony car stereo, about two days of music on random shuffle, with no comercial brakes or moderators talking BS ;-)
And in/near urban areas with high traffic density I can activate the TA on the Sony for any traffic warnings.

 

[Doug Hicks]

Dang. All I want is everything; Three or four FM stations and a couple clean AM sports stations without paying a monthly service fee is all. I built a wood and fabric experimental airplane that required an aluminum ground plane for the com radio to work properly. Maybe I can just make a pair of tinfoil underware and run an auto antenna up my back, inside my jacket!

 

[ST1100Y]

LOL! Just stuff a thing like shown here under the fairing and go ride!

But the mental image of your ST dragging a DIY aluminum foil kite behind is pursuing ;-)

 

[Tom Mac 04a]

The

must an aerial (in real nothing then a conductive rod) have a specific length, matching the frequencies its supposed to operate on

A mid freq antenna for the FM band is about 29 inches for a 1/4 wave antenna...( just easy math )... But, you will need some sort of ground plane to make it work well. If in the panniers, you can add metal screening/copper tape/aluminium tape inside to help out but still sometimes have problems. One of the few places I've seen antennas ( 2m/cb/fm) work well is on the back of a good ground plave/ grounded to frame is off of a tail rack. ( i've installed several ).
Short rubberize antennas are always a compromise and usu don't work for weak reception.

For those hams out there... I run many QRP contests and tho power is small , I run the largest antenna I can to get the best possible signal!... one case where bigger is really better!

 

[ST1100Y]

One of the few places I've seen antennas ( 2m/cb/fm) work well is on the back of a good ground plave/ grounded to frame is off of a tail rack.

+1 and suggested in #3

But while you're in the line:
what would be a good aux aerial for a PMR 440 (446,000–446,100 MHz), AFAIK 168cm or a factor of that lenght should be used, but I can't seem to find a proper eqivalent over here to be canibalized for that.
On my civil ST I've a hidden antenna for the Kenwood, made of Ethernet cable ;-) but need an appropiate rod for decorative function on rear gantry of my '94.

 

[snowmoer]

When I had my PC 800 I put in a car stereo in trunk. I used a 1200 Gold Wing radio antenna. It would pull in both AM and FM stations fairly well. It was mounted to the bottom of the plastic trunk, so I added a ground wire from the mounting bracket to the sub frame. I went with the GW antenna as it was made for a motorcycle, and the price was not that much more than a good car antenna. Plus it came with a mounting bracket. I would have had to make one for a car antenna.

It worked for me. If you went with this setup, you could mount it to the bottom of the rear rack.

 

[Tom Mac 04a]

The basic formula for a half wave antenna is 468/freq(mhz) = lenght in feet.

So a quarter wave ( most auto type verticles ) antenna is 234/freq.... or 234/466=aproc .5 feet or 6 inches...

If you looking for an antenna in the PMR, many ham antennas for 70cm banf (440mhz) will fill the bill as its pretty close maybe .03 feet longer... you can always nip off a short peice to lower the freq ( longer antenna=lower freq )... think alone the lines of an old type mobile cell hone antenna.

like for $12;

http://www.amazon.com/ExpertPower®-...d=1357760336&sr=1-14&keywords=440+mhz+antenna

 

[ST1100Y]

Thanx for confirming!

I was figuring a 2m/70cm dual band antenna might cover it, but their not realy common over here... (radio licencing and regulations are kinda strict here...)

Now to find one for solid mount on the P-spec rear gantry.
The Nagoya S-45-B seems right, will need to check if base and cable are included.

And now back to AM/FM aerials for stereos

 

[Doug Hicks]

I used a 1200 Gold Wing radio antenna. It would pull in both AM and FM stations fairly well. It was mounted to the bottom of the plastic trunk, so I added a ground wire from the mounting bracket to the sub frame. I went with the GW antenna as it was made for a motorcycle, and the price was not that much more than a good car antenna. Plus it came with a mounting bracket. I would have had to make one for a car antenna.

It worked for me. If you went with this setup, you could mount it to the bottom of the rear rack.

This may be the ticket. I wanted the clean look of a hidden antenna but that sure didn't work. I wondered too if I used an antenna like yours, if I could lay it horizontal, under the seat.

 

[ST1100Y]

...if I could lay it horizontal, under the seat.

Not the ideal position, mind that your body shields RF (bodies can do that...), which is why I'd suggested putting it into the front cowl.

But on a different note: have you checked yet if that thing even has proper reception at all, like by sticking a 2ft piece of stranded or clothhanger wire into the centre of the antenna connector and trying to tune in stations then?
Not that in real that stereo is broke, keeping you chasing ghost...

 

[st1300r]

This may be the ticket. I wanted the clean look of a hidden antenna but that sure didn't work. I wondered too if I used an antenna like yours, if I could lay it horizontal, under the seat.

The horizontal or angled position might work ok iirc a lot of commercial fm stations use circular polarity but it needs to be away from metal. The bike frame is gonna shield the antenna under the seat and really screw up the omni directional pick up pattern.

 

[Doug Hicks]

Yea, that figures. All I know for sure about wiring is that there is magic smoke inside the insulated cover and if you let the magic smoke out, it stops working! I know less about how radio works. I did ask Jensen Radio for an antenna recommendation, telling them how much I like the features of the radio and how much nicer it would be if the AM and FM buttons produced stations.

I mounted the radio in the center of the handlebars, trying to keep the look of the bike intact. It may be time to put my vanity back in the drawer and accept 'stuff' hanging off the clean lines of this sport touring bike. Anyone know where I can buy a fox tail?

 

[Doug Hicks]

Not the ideal position, mind that your body shields RF (bodies can do that...), which is why I'd suggested putting it into the front cowl.

But on a different note: have you checked yet if that thing even has proper reception at all, like by sticking a 2ft piece of stranded or clothhanger wire into the centre of the antenna connector and trying to tune in stations then?
Not that in real that stereo is broke, keeping you chasing ghost...

I missed your post earlier. I'll try both the coat hangar and placing the 'hidden' antenna out in the open. If the existing antenna works up front, now would be prime time to place it while I have all the plastic off from replacing the steering stem bearings. It will be a while from now though. I'm jumping in to the alternator upgrade and leaving the radio off the handle bars until I put a couple miles on the front end and get to re-torque the stem bearings.

 

[hoowasat]

I installed a Jensen JHD910 on my commuter ...

Good luck with your antenna search. I bought a few cheapies & tested them for reception while parked in the garage. Oddly enough, the ugly "rubber ducky" antenna won that unscientific test. I also have a Jensen JHD910 radio, and one neat feature I stumbled upon is the "auto-on" when NOAA issues a weather alert. A few times while riding and listening to the XM radio through my Garmin Zumo 665, I heard some beeping and discovered the Jensen had turned itself on. So make certain you wire it to a switched connection because when it has power, it can turn on by itself.

 

[Doug Hicks]

Good luck with your antenna search. I bought a few cheapies & tested them for reception while parked in the garage. Oddly enough, the ugly "rubber ducky" antenna won that unscientific test. I also have a Jensen JHD910 radio, and one neat feature I stumbled upon is the "auto-on" when NOAA issues a weather alert. A few times while riding and listening to the XM radio through my Garmin Zumo 665, I heard some beeping and discovered the Jensen had turned itself on. So make certain you wire it to a switched connection because when it has power, it can turn on by itself.

Yep, I wired mine through the switch. I like everything about the radio except the reception. I found an online store that advertises "satisfaction guaranteed". I haven't contacted them yet to see if that includes installed items...

 

[VFR]

Most everything has already been said except that FM is largely line-of-sight. The farther you are from the station & anything between you & the station can affect reception. Even in the city, tall buildings, tunnels, etc. can kill reception.

AM on the other hand, can bounce. Years ago I used to listen to a station in OK City all the way from NM to CA. It is fickle however, & depends on cloud cover & other mysterious factors.

As others pointed out, the antenna works best standing up in the air. Those hidden antennas don't work very well even in cars n the city.