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Problems of frequency control.

L Edge

Elite member
#1
Back before 2.4 times, there were a fixed number of 72 megahertz slots that you could fly on. The range allowed certain channels for cars, airplanes and that was all that was allowed.

So in a club situation, it meant there needed to be control of only one pilot turning on their equipment and using it. If another pilot turned on his equipment when you are flying on the same frequency, chances are the transmitter signals did not match your servos, causing you to be "shot down" and your plane could be wounded or total destroyed. The usual method to prevent that was to place a clothes pin on that frequency board, so it identifies that you do not use this channel until the person quits flying and shuts off and takes that pin off. So if a pilot arrives at the field and forgets to check the freq board and powers up, your beautiful model can vist the ground gods rather quickly.

If you had a large gathering at the club field, and with the limit number of freqs, you might have 4-5 pilots all on the same frequency, that means you fly very few times during your stay. A flight from start to shutdown averages 10 to 15 min.

If you entered competition where you have 2-3 flightlines, certain combos of frequencies could also down your airplane if the harmonics were just right. Also, if you were going to meets around the country, there were certain freqs that could not be used due to interference from local electronic equipment. So it meant you need different crystals for your receivor and you would have to set up you plane on all new settings.

Last, if the neighbor didn't like the noise and knew electronics, all he had to do generate a signal in that same range RC equipment was on and cycle it, and it forced a bunch of AMA clubs to relocate due to interference.

Hooray for 2.4!!!!!!!!!!
 

JasonK

Elite member
#2
Last, if the neighbor didn't like the noise and knew electronics, all he had to do generate a signal in that same range RC equipment was on and cycle it, and it forced a bunch of AMA clubs to relocate due to interference.
and if the AMA club had a HAM or other person with signal troubleshooting skills, they could fox hunt that down and sick the FCC on them for intentionally causing interfereance (not sure how likely that would be to have happened).
 

mdcerdan

Elite member
#3
As more and more are flying 2.4, we old school 72MHz guys have less and less interference. Last time I checked the channel monitor at my local field, my 58 channel was the only one.
I was puzzled to see the other pilots gather around me when I was flying. It turns out everyone looks at the VCR tape I tied to the tip of my antenna to check wind directon. :LOL:
 

mdcerdan

Elite member
#5
Not everyone is going to know what 72 MHz or VCR tape is.
They are going to be completely lost when we start talking about escapements, narrow banding and gold labeling.
Haha, so true. I miss the good old days when I was a boy and my Dad flew his 3 meter gliders with a Kraft and ProLine Tx.
 
#6
Haha, so true. I miss the good old days when I was a boy and my Dad flew his 3 meter gliders with a Kraft and ProLine Tx.
i just bought a receiver for an old 35mhz jr propo transmitter.... and boy you can get some really neat 35 or 72mhz transmitters for cheap... plus the receiver i bought only cost me $3 for a 6channel.... awesome...
 

L Edge

Elite member
#8
and if the AMA club had a HAM or other person with signal troubleshooting skills, they could fox hunt that down and sick the FCC on them for intentionally causing interfereance (not sure how likely that would be to have happened).
They did, answer was, prove to us(FCC) that they were the the suspect.
 

mdcerdan

Elite member
#9
i just bought a receiver for an old 35mhz jr propo transmitter.... and boy you can get some really neat 35 or 72mhz transmitters for cheap... plus the receiver i bought only cost me $3 for a 6channel.... awesome...
Yes, 72Mhz stuff is dirt cheap now. I had my second Futaba T7CAP for the equivalent of $13. Even the original NiCd pack works fine. 72Mhz gear is good enough for me.
 

L Edge

Elite member
#10
Haha, so true. I miss the good old days when I was a boy and my Dad flew his 3 meter gliders with a Kraft and ProLine Tx.
When my son and I joined up with JR, what trash talk we had to deal with for years. Going against Kraft was tough until they saw the JR equipment was just as good and stood up even when dealing with racing speeds of 200 mph.
 
#13
plus as an advantage the 35mhz or 72mhz bands do not have as much interference as 2.4 has.... think about it what new modern device doesn't have a wifi option... wifi is 2.4.....
 
#15
okay so just a question..... do you think that a standard 35mhz crystal that i can purchase from an electric components shop would work as a crystal in a 35mhz radio + receiver?

personally i think that it would because when you look at the rc crystals they are pcb crystals glorified with a piece of tape on them...
 

Bricks

Master member
#16
To help alleviate the 72 & 35mhz transmitter problem any transmitter brought to the field got impounded before you even unloaded any planes.
 

Piotrsko

Elite member
#18
okay so just a question..... do you think that a standard 35mhz crystal that i can purchase from an electric components shop would work as a crystal in a 35mhz radio + receiver?

personally i think that it would because when you look at the rc crystals they are pcb crystals glorified with a piece of tape on them...
You also need to know the transmit and recieve offsets, possibly a couple of other parameters, but Futaba had instructions for their ham frequency radios back years ago that apply. Something like base frequency minus the ic frequency for the recieve rock and I think the transmit rock is off by some other factor too. Btw: in 'Murica, the FCC moved a bunch of stuff after the spectrum reallocation such that many old 72 Mhz channels are now in the middle of high powered business communication. 72.400 to.800 is now in center of the school communication channel in my neighborhood
 
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#19
You also need to know the transmit and recieve offsets, possibly a couple of other parameters, but Futaba had instructions for their ham frequency radios back years ago that apply. Something like base frequency minus the ic frequency for the recieve rock and I think the transmit rock is off by some other factor too. Btw: in 'Murica, the FCC moved a bunch of stuff after the spectrum reallocation such that many old 72 Mhz channels are now in the middle of high powered business communication. 72.400 to.800 is now in center of the school communication channel in my neighborhood
yea i just realized that the proper jr propo crystals are the same price to ship to me from the uk... as ordering some from an electronics store...... the disadvantages of living out in the country side.
but i guess that i should just stick with the correct chips... for the correct thing..

although maybe i will revisit this idea soon... buy two of the same chips and see whether they work together if so then i have a cheap source for 35mhz crystals... 0.5$ per set....

advantage to living in the country side... no one cares what frequency you run your rc stuff on.... there is no school or business near me.....

except the armed response services..... hmmmm how about sending them.... numbers anywhere between 1024 and 0.... from my tx as i drive past...:devilish:...
ooooh wait i don't want to go to jail during covid......... or ever
 

Piotrsko

Elite member
#20
Umm nope, the comment about the school wasnt regarding interception of an illegal signal, it was for when they key up and crash your plane since a 25 watt signal on a good antenna drowns a 100 milliwatt signal. However, since the crystals are cheap, it might be worth buying a set and see if they work.