HELP!! DO AM RADIOS NOT WORK ANYMORE????

[longboardnj]

I'm going nuts and I can't find any info online about this. I've been trying to use some of my am radios with no luck. No range and a lot of glitches. I tried 6 radio combos and nothing seems to work besides my futaba attack r stick radio in my stock super clod buster with mechanical speed controller. Even that has about a 10 yard range. Any help or thoughts on this subject would be great!

[GoMachV]

Nope AM still works fine. Just gotta make sure crystals are correct brand and installed properly, antennas aren't cut, and that both tx and rx are same brand and tuned for correct bands

[Incredible_Serious]

I still have (and use) a plethora of AM radios. There are a number of possible range and interference issues, but most of the time they should work on the bench at least... here's some things to consider:

Range and interference:
- Has the receiver antenna wire been cut, chopped, shortened or damaged in any way?
- Does the motor have noise reduction capacitors in place?
- Is the receiver too close to the motor, or is the antenna wire run close to the motor?
- Are you using the wrong frequency crystals in the radio gear ie. 29MHz crystals will work in 27MHz gear, just not well...
- Are your transmitter batteries weak, or is the battery compartment dirty?
- Is your transmitter aerial in good condition?

Not working at all:
- Are the crystals matched? Are they in their correct place (TX crystal in the TX and RX crystal in the RX)?
- Are you using FM crystals in AM gear? Or an FM transmitter with an AM receiver?
- Is the receiver wired correctly? Remember that some earlier radio gear (Acoms, Sanwa, KO etc.) was wired signal-negative-positive, whereas most stuff (Futaba and their copies, JR, etc.) is wired signal-positive-negative.
- Are you trying to power a receiver without BEC built in with full battery power?
- If steering is working but throttle is not (for example), try switching the servo and the ESC, and work out if it's a receiver problem or a servo / ESC issue.


The best way I've found to test things is by the Single Replacement Method.
1. Get a FULL set working perfectly - Transmitter, receiver, power source (ie. ESC or battery), servo, crystals, and motor.
2. Replace ONE ITEM ONLY and retest. This way, you will be able to quickly find weak links, broken and problem items.
3. Test one item as much as you can, before going on to the next part. For example, I will line up half a dozen or more servos, receivers, crystal sets, transmitters, and then run through an entire group of items first.
4. MARK anything that is broken / 'dodgy', not marked for frequency, or not as you would expect.... this saves you having to do it all again next time! I have all my transmitters and receivers marked with frequency, polarity, and status, if they are not marked as such by the manufacturer.

Let me know if this helps..... I have sooooo much AM / FM gear, that all works well enough for me... and the simple testing regimen and especially the marking (point 4 above) have saved me a LOT of hassles.

Alex

[DMAT]

one of those glitch busters that is basically a capacitor that plugs into the reciever can help too.

double check your battery terminals on the transmitter too. If the power isnt adequate, you might need to replace some battery tabs. Digikey stocks all kinds of replacements.

speaking of AM, I had the weirdest glitch going on. When inside a building, When my car got into a certain corner of the track, The steering would force turn itself and I had to get up real close to it to make it straighten back out. Nobody at the track could figure it out and It didnt happen anywhere else either.

[tamiya]

where have they been stored?

If you're in a damp area and they've been sitting in a garage/garden shed on damp concrete floor
its not unknown that AM radio gear can get water damaged. Most older gear have ferrite stacks
for tuning, these get corroded and the tune goes out of whack.

They can be retuned if you know a technician with a CRO but that's a dying skill nowadays.
Old gear with discrete electronic parts can be repaired if spares are available,
but not easy to find anymore.

[tamiya]

speaking of AM, I had the weirdest glitch going on. When inside a building, When my car got into a certain corner of the track, The steering would force turn itself and I had to get up real close to it to make it straighten back out. Nobody at the track could figure it out and It didnt happen anywhere else either.

gotta ask yourself... who's next door? Could be some govt agency or IBM's secret R&D lab...

What channel were you running? Some freqs more susceptible than others, like Blue #6 (27.245)
if you were near some powerful CB base station like a truck depot or a taxi despatcher.

[longboardnj]

crazy but ive been doing this hobby for over 30 years and i think ive been doing radio stuff wrong .

1.antennas cut or damaged. i thought that would just shorten your range a little. no? if a antenna is cut cant you just sodder it back and its ok? ...................

2." tx and rx same brand and tuned for correct bands" i dont understand this? i have a bag of crystals i just match numbers... does it matter white 79 and yellow 79 where they go?. ...

3. "- Are the crystals matched? Are they in their correct place (TX crystal in the TX and RX crystal in the RX)?" how do i know how to match radio/rec/crystal?

4."Are you using the wrong frequency crystals in the radio gear ie. 29MHz crystals will work in 27MHz gear, just not well."im not sure how to tell

5.i always just swapped crystals to different remotes.. do remote #s matter like one remote can only use 70-79? if this is true how do i tell the crystal tabs #s on all my remotes have been removed .
thanks for the help i dont have the cash to buy more remotes i have 6 good am radios id like to use them

[GoMachV]

1- as long as the length is correct, you should be ok but you need to know the proper lengths
2- crystals are pairs of a TX and RX and differ between makers. A futaba TX crystal with a Airtronics RX crystal on the same channel still wont work properly.
3- look for a TX or RX on the crystal. Futaba narrow band receiver crystals have the yellow label
4- look on the transmitter, it will say if it was tuned for 27 or 75 band. Same with the receiver. Aftermarket receiver antenna color will sometimes vary to denote the band also
5- you should be ok as long as they match band (27.XXX or 75.XXX)

[Incredible_Serious]

crazy but ive been doing this hobby for over 30 years and i think ive been doing radio stuff wrong .

1.antennas cut or damaged. i thought that would just shorten your range a little. no? if a antenna is cut cant you just sodder it back and its ok? ...................

I've seen a lot of information over the years about older receivers having a 'tuned-length' for their receiver wire. This would mean that it would be a specific length from the factory for a reason... trimming it may lessen range significantly. However, if you rejoin the wire, and the connection is strong electrically, then there should be no negative impact. With respect to 'damaged', sometimes the antenna wire may be damaged, but not appear broken. This can be especially where it comes out of the case. Just good to check the wire it's entire length, by eye and / or with a multimeter (if possible).

2." tx and rx same brand and tuned for correct bands" i dont understand this? i have a bag of crystals i just match numbers... does it matter white 79 and yellow 79 where they go?. ...

I have experienced some radios (KO, I'm looking at you here!), where you needed the specific brand crystals for the gear to work.... however for me, I've only experienced it once, and the radio set was FM, not AM.

3. "- Are the crystals matched? Are they in their correct place (TX crystal in the TX and RX crystal in the RX)?" how do i know how to match radio/rec/crystal?

Matched just means using, for example, 27MHz AM transmitter crystal in a 27MHz AM transmitter, and 27MHz AM receiver crystal in a 27MHz AM receiver. The transmitter crystal may be marked as TX, or may have a marking like TA26.995 meaning TX AM 26.995MHz. The appropriate receiver crystal may be marked as RA26.995, RX AM 26.995, or more likely RA 27.450, as receiver crystals can be marked with their offset value (TX + 0.455MHz) or their transmitter value.

4."Are you using the wrong frequency crystals in the radio gear ie. 29MHz crystals will work in 27MHz gear, just not well."im not sure how to tell

Check the numbers as per number 3 above - 72MHz crystals are less likely to work in 40MHz or 27MHz systems.

5.i always just swapped crystals to different remotes.. do remote #s matter like one remote can only use 70-79? if this is true how do i tell the crystal tabs #s on all my remotes have been removed .

This is where I mark what a remote is for ie. AM27, FM40, FM29, etc. That way, I know whether it's AM or FM, and what range crystals to use with it.

thanks for the help i dont have the cash to buy more remotes i have 6 good am radios id like to use them

I'm with you, mate.... I have so much older gear, I see no use in buying more new whiz-bang 2.4 stuff. rather save the money for cars.... or beer!

Hope that helps....

Alex

[longboardnj]

ok great this helps alot.. looks like alot of my stuff is ok and i understand am much more.. mostly everything i have is futaba so it matches the 1 problem i see is maybe the cheap aa batteries are not strong enough and the crawlers have the ant running by the motor.. thanks for keeping it classy guys and not busting on me about being in the hobby for 30+ years and having newbie ?s..

[Incredible_Serious]

thanks for keeping it classy guys and not busting on me about being in the hobby for 30+ years and having newbie ?s..

I was just getting to that.....

[EvolutionRevolution]

2." tx and rx same brand and tuned for correct bands" i dont understand this? i have a bag of crystals i just match numbers... does it matter white 79 and yellow 79 where they go?. ...

I have experienced some radios (KO, I'm looking at you here!), where you needed the specific brand crystals for the gear to work.... however for me, I've only experienced it once, and the radio set was FM, not AM.

FM radios and receivers need to use the same brand of crystals as they are. So KO transmitter takes a KO crystal, KO receiver also a KO crystal, Futaba transmitters and receivers a Futaba crystal, etc.
However, if the TX and RX are different brands, they can work together if they are on the same frequency. So a 40.675FM Hitec transmitter (with Hitec crystal) will work with a 40.675FM Futaba receiver (with Futaba crystal).

AM radios and receivers are not as sensitive to crystal brand.

By the way, if someone can tell me where I can still find 40MHz FM Sanwa crystals, I'd be very grateful.

[Bormac]

Funily enough Ive recently discovered some 'issues' with my AM radio gear. The transmitters to be exact.
I wanted to set my sons Hotshot up with a twin stick radio so I went with an old radio. I found that it would not allow me to tune the current batch of Tamiya ESC units and could not work out why.
After someserious head scratching and investigating I worked out that all of my twin stick AM radio's potentiometers were'nt too functional. I finaly found out that my nib JR BEAT2 radio worked andall the others didnt.

So my question is, do these potentiometers wearout or become less operational???

[jwscab]

Am is a nightmare because of its wideband sensitivity. For sure the tx or Rx after all these year may need a tune. Shock vibration humidity and temp all play a role in degradation over time.

As for potentiometers they absolutely wear out over time especially if it's a carbon track vs. Wirewound. Carbon track is much cheaper so was typically used.

You should never change the length of the Rx antenna.

Am is susceptible to ac motor noise particularly so in the case where your car flipped out at one place n the track probably got near a fan motor or ac compressor or something similar.

[Kyoshojoe]

florescent light magnetic ballasts can play havoc too especially if they are going bad