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Posted by eyeflyhelis on 11-21-2017 03:46 AM:
anybody still using them, if so what for? does it seem like there is less interference now that most people have gone to 2.4g?
This weekend i took my last FM/ PCM radio out of a heli. been flying 2.4g since it came out but never swapped over my raptor 50 helicopter. just took my jr 8130 pcm out. thinking about selling or trading it but i know i wont get much value for it so i was looking for some else to do with it.

only you have the power to make no difference!

Posted by EEngineer on 11-21-2017 03:55 AM:
Because people don't have money to spend to upgrade....and they still work due to FCC regs.

There are also collectors that would be more than happy to have your old FM radio systems....and might even buy them for a small sum.

FWIW

Logo 600SXs, 800XX, TDR IIs

Posted by InvertedDude on 11-21-2017 03:57 AM:
eyeflyhelis
Use your FM for long range FVP. 2.4 ghz doesn't go as far as an FM will go in open skies. Anyone correct me if I am wrong?

I like your JR 8103! I had one, I sold it to upgrade. Dumb on my end!
Posted by EEngineer on 11-21-2017 04:12 AM:
FM has an unusual characteristic called "capture ratio".

Which is a measure of how well an FM RX will "lock" onto an FM TX.

Whereas, with AM transmission, you have all experienced...while driving...that you can "hear" several weak AM radio stations at one time.

So, AM will provide max range...lol(more interference)....FM perhaps 2nd...with 2.4 Wifi a distant 3rd....

All depending upon the type of Tx and Rx antenna system used.

In general

FWIW

Logo 600SXs, 800XX, TDR IIs

Posted by ICUR1-2 on 11-21-2017 04:23 AM:
I would trust FM in a foamy or an fpv drone

fm goes through buildings easier than 2.4
As for range that depends on system tx/rx.

Long range fpv uses uhf ~ 30 Km vs 2.4 ~ 3Km.
I never looked into fm as I started at the same time as spektrum.

spending time, paying attention

Posted by EEngineer on 11-21-2017 04:30 AM:
I don't "trust" anything....or anybody....without knowing about the situation....

That was an odd recommendation....LOL

Logo 600SXs, 800XX, TDR IIs

Posted by spaceman spiff on 11-21-2017 05:18 AM:
I just picked up a couple old JR 6102s for just over 20$ each on e bay. Not fancy, but one of my old favorites. Still work great, and most of my planes already have the recievers for it... Every bit as much fun now as it was 10 or 12 years ago. Folks pay a bit more for your 8 channel.

I picked up a Futaba T8FG. in 2.4Ghz FAST tech a few years back. Good stuff, but It is also outdated now.

Nothing wrong with the old stuff if it is doing what you need it to. Check or replace the battery if you decide to continue to use it.
Posted by EEngineer on 11-21-2017 05:41 AM:
Usually the TX batteries are the issue.

Just keep the original battery plug...because it's easy to obtain
a suitable replacement battery....but the plug can be harder to find.

Just solder the old plug wires on the new batt pack wires....

Logo 600SXs, 800XX, TDR IIs

Posted by eyeflyhelis on 11-21-2017 06:01 AM:
I never realized that fam had a better range. I have flown by 2.4 9103 and 9303 S as far as I could see I never had an issue. That being said back in the day with my old 347 X and then my 8103 I did the same thing so I never considered range to be an issue.
Currently I also have a DJI mavic Pro which I fly 1950 ft away according to the screen and that's to boil for that I can't even see that and never had an issue.

only you have the power to make no difference!

Posted by eyeflyhelis on 11-21-2017 06:08 AM:
I just looked on eBay and there is a lot of 8103 radios on there and people are trying to get $350 for them but none of them have any bids. I have to dig through my stuff I'm pretty sure I have a 9103 FM radio someplace, I'll hold on to that one that was one of my favorite reviews thanks for the advice guys

only you have the power to make no difference!

Posted by EEngineer on 11-21-2017 06:46 AM:
1950 feet is less than 4/10's of a mile....

The current altitude record...set by Maynard Hill...using AM is around 30,000 feet....

Logo 600SXs, 800XX, TDR IIs

Posted by ICUR1-2 on 11-21-2017 01:13 PM:
Ahh much better with out all the useless posts.

spending time, paying attention

Posted by helitom on 11-21-2017 03:53 PM:
As to value - they have virtually none. Looking on Ebay, as I frequently do, the old FM/PCM radios get listed with starting bids of 0.99 cents. They most often get zero bidders.

Oh yeah, I still fly two Futaba 9Z's with the FASST RF modules in foamys, gliders, ect... All my helis have new Futaba systems. All the other old stuff got deposited in the green filing cabinet that is located just outside my garage and gets emptied out once a week.

The older I get, the fewer things seem worth waiting in line for.

Posted by 870heli on 11-21-2017 05:15 PM:
I loved the 8103 back in the day. I like everyone am flying 2.4 now.
In last weeks I have been getting hopped up on having some old classic heli's. I picked up two new old heli's and a new JR 783 radio that I am going to use to fly they with. Just for fun. I never thought that I would be buying FM's ever again.
Hind sight tells me I would keep it for what you can sell them for.
Posted by eyeflyhelis on 11-21-2017 05:49 PM:
helitom
All the other old stuff got deposited in the green filing cabinet that is located just outside my garage and gets emptied out once a week.
That only happens after a rough day usually. And I hate those days

only you have the power to make no difference!

Posted by eyeflyhelis on 11-21-2017 05:51 PM:
30000 feet!!!!!!! :0 heck I never thought that was possible with a radio. He must have have one hell of a good set of binoculars

only you have the power to make no difference!

Posted by eyeflyhelis on 11-21-2017 05:54 PM:
870heli
Hind sight tells me I would keep it for what you can sell them for.
I threw it up on the trade for him to see if anybody would bite on a trade for a 600 or 700 mm carbon fiber blades. I do have a few guys interested. But I look for my 9103 last night and then realized I had a 9303. So I'm going to keep that one and a couple of our 700 receivers for it

only you have the power to make no difference!

Posted by EEngineer on 11-21-2017 06:30 PM:
30000 feet
Google Maynard Hill...

Of course, his TX was connected via a coaxial cable to a Yagi antenna system....which is a form of directional antenna.

He was also using a telescope to view his aircraft.

He also had permission from the FAA to perform this feat.....

Among the difficulties was to keep the avionic equipment working....due to the intense cold at altitude. So he had to use a heating system within his aircraft, which "ate" into his power budget.

Another famous feat that Hill accomplished was to fly across the Atlantic Ocean.....nonstop....using an autopilot system that he developed.

FWIW

Logo 600SXs, 800XX, TDR IIs

Posted by Pistol Pete on 11-21-2017 06:50 PM:
old fm radios
anybody still using them, if so what for?
JR8103 demoted to SIM duty and yes! it can handle a 3S LiPo.

Sadly they dont do well with a gasser heli and mainly why I migrated (and not upgraded) to 2.4GHz.

As for range, the higher the frequency, the shorter the distance.

72MHz range can be as far as 5 miles LOS and forgiving around buildings at much shorter distances unlike 2.4GHz which is shorter than 1.5 miles if not mistaken and going around a building is going to be a quest. That plus 72MHz radios output are as high as one watts versus 2.4GHz at one tenth of a watt.

72MHz signal degrades and your model will act weird and or glitch while 2.4GHz has fail safe and you wont even know you are not in control unless you programmed something unusual to happen other than keeping last know signal. So if you happen to be flying a straight line away from you and lose signal, good luck.

Downside to 72MHz is its prone to interference by someone else in same channel unlike 2.4GHz which not only has channel hopping but now has model match and will only respond to one radio.

So if you keep your 72MHz, you can have your cake and eat it too.

~~Enjoying the hobby one flight at a time~~

Posted by jharkin on 11-22-2017 12:07 AM:
It seems like AM/FM/PCM radio have now been put in the same category as nicad batteies and analog servos with newbies convinced that their heli will crash if they tried to use it ...

[this forum needs a facepalm smiley]
ICUR1-2
I would trust FM in a foamy or an fpv drone
...
I never looked into fm as I started at the same time as spektrum.
FM will work just fine in any model you want to use it in, no reason to be scared of it. Its a well proven technology we have used forever in RC... the only major downside is that its not spread spectrum.
eyeflyhelis
30000 feet!!!!!!! :0 heck I never thought that was possible with a radio. He must have have one hell of a good set of binoculars
I'm missing some replies due to having some annoying members on block. I assume you are referring to Maynard Hill's altitude record. They used high power naval binoculars on a tracking mount, along with radar to follow it.

BTW, that was in 1971 and I'm pretty sure it was AM radio , not FM. Old Kraft and Cirrus sets.

https://www.dmfv.aero/files/Flying-Models-Jan-1971.pdf
Pistol Pete
Sadly they dont do well with a gasser heli and mainly why I migrated (and not upgraded) to 2.4GHz.
???? FM works just fine on gas. I flew FM and PCM on gas airplanes for years and years... never had a single problem so long as you know how to properly isolate the receiver from the ignition.

The main advantages of 2.4 are spread spectrum (no worries about freq pins and shoot downs) and the increased bandwidth that allowed us to move beyond the 9 channel limitation of AM/FM/PCM.

-Jeremy
Whiplash-G
Helix 700G
T-Rex 450 fbl conversion
alot of planks

Posted by ICUR1-2 on 11-22-2017 12:16 AM:
Couldn't a coded signal be used in fm similar to the protcals of today.
or is the fm bandwidth not fast enough to communicate the coded signals.

spending time, paying attention

Posted by EEngineer on 11-22-2017 02:00 AM:
Hill was using AM....so what? Maybe I also should have said optical enhancement technique so no "nitpicking" about telescope vs binoculars....jeez.

2.4 GHz is just the frequency band used today....

You're conflagrating two different things....

Spread spectrum can and is used with other frequency bands....like UHF, etc....GPS uses "spread spectrum" on two different frequency bands.

And there are many types of "spread spectrum" techniques.

The facepalm can be left at HF where it belongs.....LOL

BTW, with AM transmission, half of the TX output power is used simply to send the "carrier" which sends no info....the other half is split into the upper and lower sidebands, each of which has 1/4 of the carrier's power.

Not the case with FM.

Logo 600SXs, 800XX, TDR IIs

Posted by eyeflyhelis on 11-22-2017 03:54 AM:
i only switched back in the day because of noise in the 450 helis. i never had an issues with gas or nitro, that was before large electric helis were popular

only you have the power to make no difference!

Posted by Pistol Pete on 11-22-2017 08:31 AM:
jharkin
FM works just fine on gas. I flew FM and PCM on gas airplanes for years and years... never had a single problem so long as you know how to properly isolate the receiver from the ignition.
My issue was with my gasser heli. It glitched and going to SPCM helped. (JR8103 & Radical 20) Unlike a plane, there isn't a whole lot of real estate to separate electronics and cables as far away as possible from the "sparky" end of the engine.

~~Enjoying the hobby one flight at a time~~

Posted by Dyehard on 11-22-2017 12:43 PM:
Maynard Hill's last altitude record was set on September 3, 1970. The actual altitude reached was 26,990 feet. I recall reading with great interest the article on that in MAN, as well as his other record flights when they happened. One item of interest, on the way down, radar lock on the plane was lost and they lost it through the telescope as well. I could be wrong, but I think I remember that he put it in a spin to bring in down. It was down to only a few thousand feet when they spotted it and then only because it was covered in mylar film and someone on the team saw the sun reflecting as flashes on the film, well away from where they expected the plane to be. This was before Monokote. Maynard Hill was an exceptional modeler, there have been and probably will be few like him.

Allen Dye

Posted by EEngineer on 11-22-2017 04:19 PM:
Maynard Hill was legendary.

A true pioneer of model aircraft and radio control almost before the invention of ICs.

He also made an auto pilot system for RC aircraft.

Logo 600SXs, 800XX, TDR IIs

Posted by w8qz on 11-22-2017 04:45 PM:
ICUR1-2
Couldn't a coded signal be used in fm similar to the protcals of today.
That is essentially what is known as 'PCM', although without the 'bind' aspect. However at 72 MHz the allowable bandwidth is quite limited, compared to what is allowed at 2.4 GHz.

"The helicopter is much easier to design than the aeroplane, but is worthless when done."

Posted by EEngineer on 11-22-2017 05:21 PM:
In addition to the fact that since the 90's, RF technology has advanced so rapidly...it's astounding.

So we are all reaping the benefits of this....

Frequency pins are a relic of the past....dinosaurs....fossils, even.

Logo 600SXs, 800XX, TDR IIs

Posted by jschenck on 11-23-2017 01:36 PM:
really too bad that our hobby/industry didn't adopt the DSS protocols into our existing dedicated 72Mhz radio frequencies. I'm sure that at this point the FCC is looking at a reclamation process to get that valuable spectrum out of our hands. Missed opportunity on our side.
Posted by Four Stroker on 11-23-2017 02:41 PM:
Gassers never worked with the JR single conversion receiver with the gray crystals. The solution was always to go with the dual conversion receiver which had the red crystals (plastic distinguishing cover). The dual conversion worked fine. EE, I am not saying that dual conversion was the solution but that the dual conversion receiver worked and the single conversion one did not.

Just because you are not getting glitched with 2.4 does not mean you are not losing packets. CRC's work, generally. I worked out that a few bad packets an hour can get through with a 16 bit CRC. I don't think people notice a 10 ms glitch.
Posted by EEngineer on 11-23-2017 04:30 PM:
I had the single conversion JR system....a JR10X.

Worked OK with plank engines....wasn't into helis then.

For the benefit of others, dual conversion would 1st "down convert" the received signal by "mixing" it(RF multiplication) with a 10.7 MHz oscillator....and then filtering the resulting signal.

Then, for the 2nd conversion, a 455KHz oscillator would be used to "down convert" the 1st stage signal....and filtered.

Then the data for the servos would be "extracted" and used to control them.

Back then, without attaching all sorts of cumbersome electronic test equipment to the whole setup, there wasn't any way to see what transmitted info was dropped.

So...if you felt "glitches" when flying, something bad was about to happen.

Land quickly!....

Logo 600SXs, 800XX, TDR IIs

Posted by Four Stroker on 11-26-2017 12:37 AM:
The 72 MHz frequencies are used in the construction industry. They were always more important that the entire RC community. Antennas at 72 MHz are inconvenient. I don't think anyone in particular wants those frequencies. Otherwise the FCC would have auctioned them off. If you tune a scanner to 72 MHz you won't hear much. I flew on 72 MHz for 40 years without a glitch.

There is not enough spectrum on 72 MHz for modern SS techniques. FASST or DMSS is 3 MHz bandwidth - on each hop - and the 72 MHz band is only about 1 MHz.
Posted by eyeflyhelis on 11-26-2017 03:07 PM:
i flew gassers with the grey jr rx crystal, never noticed any issues, but i didn't do any hard flying back then. lost more gasser helis to stripped tail gears that glitches. i also ran all my antennas on a plastic tube coiled up, not sure if that helped but it seemed to work.

only you have the power to make no difference!

Posted by Four Stroker on 11-26-2017 07:13 PM:
We had 5 guys with gassers that switched to the dual conversion RX and fixed their problems with glitches. Nobody flying Futaba which had all dual conversion RX's had their problem. Plane guys had no problems with the single conversion JR.
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