How to Replace Me as FM Radio Antenna Booster?

[BFL13]

TC with car type radio and antenna. Often get garbled reception that clears up if I get near the radio.

What is needed for the antenna or whatever?

Thanks

[Gdetrailer]

wa8yxm wrote:
Re that folded wire dipole.
A folded dipole like that has an impedance of around 300 ohms
The radio is more likely "Something different" Coax is typically 75 (But not sure on auto radios.. Long mathematical story) Best reception requires a match.

If the antenna is a "Stubby" A longer antenna will help BUT if it's too "Tall" (Over 13') there is a chance it can be a problem going under a low bridge.

And for GDE trailer.. I did say they might not work.. I checked and you did a good job of explaining why.

Impedance mismatch on receive generally will not hurt reception performance very much if any.

In fact, you can plug a straight piece of wire 6" to 4' right into most antenna inputs and and get some sort of reception.

Car radios are an oddball on antenna impedance.

The coax used is 93 Ohm (RG-62) found HERE

"Product DescriptionCoax 93? RG-62A/U Type, 22 AWG solid bare copper-covered steel, semi-solid polyethylene insulation, bare copper braid shield (95% coverage), PVC jacket,CM"

The center conductor is also surrounded with Solid PE monofilament spiral around conductor.

It has been reported that typical car stereos antenna input impedance is around 100 Ohms and the typical car antenna has an impedance of roughly 36 ohms and 92 ohm coax is generally used..

Lots of impedance mismatches..

Most car preamps like the one you linked are 75 ohm which also represents a mismatch..

You are correct on folded dipole as approx 300 ohms, for that one I would be inclined to add a 300 to 75 ohm balum for a slightly better impedance match.. But, keep in mind, I was using that picture as a illustration of my struggles with indoor wire antennas which do not do very well for distance station reception.

As I mentioned, impedance mismatches on reception while not ideal generally will work OK with OK results..

Now if you were transmitting, that would be a hole nuther can-o-worms..

[wa8yxm]

Re that folded wire dipole.
A folded dipole like that has an impedance of around 300 ohms
The radio is more likely "Something different" Coax is typically 75 (But not sure on auto radios.. Long mathematical story) Best reception requires a match.

If the antenna is a "Stubby" A longer antenna will help BUT if it's too "Tall" (Over 13') there is a chance it can be a problem going under a low bridge.

And for GDE trailer.. I did say they might not work.. I checked and you did a good job of explaining why.

[BFL13]

So I got home and tested against local stations, which come in 5 by 5 or clear as a bell. So now it looks more like distance to the preferred station where I was just at in a campground up-Island. (Englishman River Falls--CBC 92.5)

I want to improve my radio set-up for getting a clear signal on that station at that campground in the future, so I will work on the suggested upgrades.

Thanks!

[Gdetrailer]

If your rig has fiberglass siding, the outside braid of the coax is most likely acting as a "counter poise" or "groundplane".

By unwinding and unbunching the coax you increased the counter poise or groundplane improving reception.

Basically as is it is the same as this..



A wire "dipole"..

I have had zero luck where I live using wired dipoles and even folded wire dipoles like this..



Since most of the radio stations I have are 40-50 miles from me..

You might need a new plan of attack, longer whip plus some metal near the antenna to act as a ground plane or counter poise..

If you can remove the ducky mast leaving the mount in place, perhaps try adding a metal rod twice the length to where the ducky was connected to see if that improves things..

[BFL13]

Thanks, got at it to try those ideas

Checked ground no diff. Back of radio mounted in a high cabinet next to stubby outside antenna at edge of roof, the antenna cable comes in and it is too long for the job so it is bunched up.

I could hear voices but too much background noise to make out what was said until I put my hand on that antenna cable and the background noise was gone. So I re-arranged how the cable is bunched and found a way where I get little noise with me standing away. It is loose so could get bad again. It used to be ok so driving must have moved it to a bad spot.

I think I need a longer outside antenna with a shorter cable or arrange the long cable so it is not overlapping on itself in a bunch so much?

[Gdetrailer]

wa8yxm wrote:
Interesting. First make sure the antenna is properly connectred.

Most Automotive antennas have what is sometimes called a Motorola connector. This is a coaxial plug where the outer connection doubles back on the coax unlike the RCA connector where the outer connection surrounds the center pin.

Look at the ends of the cables in the linked device. NOTE Pre-amps sometimes work Sometimes do not.

Another issue is proper grounding of the radio.. To the frame of the Vehicle.

Fm Car Radio Preamplifer at Amazon

"Boosters" for the most part do not work if there is little to no signal and can make reception even worse when very little signal is present..

The only boosters I have found that truly work are the ones that mount right at the antenna. Booster gets the strongest possible signal so it isn't amplifying garbage.

Boosters for car radios can be very problematic, car stereos unlike home stereos employ the same jack for AM and FM and most boosters for car radios do not amplify in the Khz AM radio band.. This means inserting a booster will result in removing all hopes of receiving any AM stations if that is you game.

The one you linked also does not amplify AM band per the specifications and one of the questions and answers posted..


Specifications:
Material: Electronic Components, Metal, Plastic
Voltage: DC 12V-24V
Frequency Range: 48-860 MHZ
Gain: 25dBi±3
Impedance: 75 ohm
Noise factor: =7dB
Output standing wave: =3
Operating temperature: -20? -- 70?
Storage temperature: -40? -- 90?
Item Length: 15.75 inches

"Claim to have am boost. the specs say 48-860 mhz. am is khz. there are no listings in your specs of this. the fm specs look great. what about am specs
Answer:
That thing is a waste of money. It made my reception worse."

I would stick to the "basics" and check to see if there is even a antenna really attached to the radio first. Often times RV manufacturers just wind up the wire behind the radio and call it good without hooking it up to an external antenna.

If there really is a connection to an outside antenna, perhaps time to replace the shorty antenna typically used on RVs with a longer antenna.. Those little short 1ft or less rubber duckies don't perform well.. typically want 4ft long whips for half decent reception but there is a catch with the longer antennas.. Your chance of striking something low height and breaking off the whip gets greater so measure carefully.

Lots of aftermarket longer antennas available, just have to figure out what will work for the mounting system you have.

Barring all that, the issue just might be the radio it's self, have had some car stereos with pretty weak tuners and the only fix for that is to replace with a better brand..

[wa8yxm]

Interesting. First make sure the antenna is properly connectred.

Most Automotive antennas have what is sometimes called a Motorola connector. This is a coaxial plug where the outer connection doubles back on the coax unlike the RCA connector where the outer connection surrounds the center pin.

Look at the ends of the cables in the linked device. NOTE Pre-amps sometimes work Sometimes do not.

Another issue is proper grounding of the radio.. To the frame of the Vehicle.

Fm Car Radio Preamplifer at Amazon