The Forgotten Frequency - 27mhz - RC Groups

The Forgotten Frequency - 27mhz

The forgotten frequency “27mhz” is still alive and well but no one remembers it or looks to it for operation of the models.

Splash

27mhz

The submariners know the drill all too well about the problems of penetrating a radio signal beneath the surface of water they wish to operate their subs in, and in all truth have found out long ago that the longer wave signals such as the 27mhz band does a pretty good job of penetrating the surface.

Back in the days of “SMOKEY AND THE BANDIT” when CB radios were all the rage, the problems of interference became almost an everyday occurrence for the RC modeler operating on 27mhz, (which by the way was the very first of the bands open to the citizens use). With the addition of the 72mhz and the 75mhz bands of crystal controlled systems into the market, the start of the migration from 27mhz frequency for the radio controlled operations began.

The next big turn in the use of frequencies for control of our models was with the use of the cell phones by everyone including the “GOOD BUDDY” truckers, clearing the dashboards of all of the old school CB radios. Along with that change came the introduction of the 2.4ghz radio systems for use in the RC control of our models. With that one move, the door was both closed and opened on the use of 27mhz frequency for RC use.

The 27mhz frequency is all but clean of any chatter or random signals and is pretty much clean and open for use for RC operations. The one thing in its favor is that because of the lower frequency, the ability for signal penetration is far greater than any of the other frequencies that are available, and as a bonus, there is little or no interference from other operators on the frequency.

So there you have it! Some food for thought! ;)

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Dec 05, 2015, 04:31 PM
Registered User
coriolan's Avatar
Unfortunately it is now almost impossible to find 27Mhz equipment with more than 3/4 channels, same thing for 75 Mhz. The 6 meter band is usable for surface use, but here too there isn't much available and you need license. Many clubs involved with submarine allow the use of air frequency(72 Mhz)for that very reason since there is a large supply of Tx/Rx in that band as everyone went to 2.4 Ghz, AMA/MAAC might not like it but there is no alternative for lack of suitable equipment. Personally I still use 75 Mhz(Ch#70)since I do have a Ch #70 module for my Eclipse-7 in combination with SombraLabs Rx which can be programmed in 72/75 Mhz band:
http://www.sombralabs.com/products.php
Dec 05, 2015, 07:13 PM
AndyKunz's Avatar
I thought you were talking about 49MHz when I read the title!

Andy
Dec 05, 2015, 07:25 PM
Just Plane Nutts
AirDOGGe's Avatar
-Double Post-
Dec 05, 2015, 07:27 PM
Just Plane Nutts
AirDOGGe's Avatar
I figured the 27mhz frequency lost favor due to the appearance of and proliferation of RC cars on the market in the late 1970s and early 80s using that band (along with 49mhz). The use of 27mhz in these toys gave the frequency a "cheap" image. People just didn't want to buy radios using them. I know back then I didn't.
Dec 05, 2015, 07:37 PM
Registered User
I LOVE & have lots of 75 MHz . Crystals. I just started doing small boats again. I have 2 about 20" subs. Will do them as only full speed to dive. The larger Skipjack & Gato get a full static diving pump system.

I also have about 10 of those small 27 MC cars. They run great. Might take a few for the small subs & boats drive systems. I like the combined steering & motor on 1 PCB.
Dec 05, 2015, 09:04 PM
Registered User
Back in the day 27mhz was not a TOY frequency like the 49mhz frequency was. The 27mhz frequency had a much further range and was at the time the only frequency for both airplane and car use known as a shared frequency.

The 49mhz frequency was mostly found in the cheap radio controlled cars with a maximum range of about 150 feet. The 27mhz frequency had the same range as the 72 & 75mhz radio systems and the 2.4ghz radios of today.

The fact of the matter is that the 27mhz signal is able to control a model behind a water fountain or a tree full of leaves, or even a wooden fence, something you would not want to try with the new 2.4ghz radio systems.
Dec 06, 2015, 12:14 AM
Just Plane Nutts
AirDOGGe's Avatar
Ah, I see.

Looks like there's a few 27mhz transmitters available on eBay, some including a receiver: http://www.ebay.com/bhp/27-mhz-transmitter
Dec 06, 2015, 01:25 AM
Grumpa Tom
Kmot's Avatar
Rich, I'm still hanging on to my Futaba FP-3PG 27 Mhz radio (also have a 75 Mhz module which I cannot legally use anymore). I have another three or four 27 Mhz stick radios as well as Rx's and crystals. Never know when they may come in handy. I sold all my 75Mhz stuff long ago, as soon as 2.4Ghz hit the scene.
Dec 06, 2015, 08:37 AM
Registered User
Is 75 MHZ not legal ?
Dec 06, 2015, 08:43 AM
Registered User
coriolan's Avatar
27/53/75 Mhz are still perfectly legal for surface use, don't know what Kmot meant!
Dec 06, 2015, 09:19 AM
Registered User
Thanks coriolan.
Dec 06, 2015, 11:23 AM
Registered User
I think what KMOT means is that the 72 & 75mhz frequencies should be checked for channel splash over by a radio technician to see if it meets and is certified with a gold label for continued use on that channel spread.
Dec 06, 2015, 11:47 AM
Submarines, etc.
tsenecal's Avatar
to paraphrase frankg... and put it in terms i can understand.

prior to 1992, radios were "wideband", after 1992 radios are "narrowband". 75mhz "wideband" are not legal, because they can cause interference on new "narrowband" radios that are using neighboring frequencies. the 27mhz modules/versions do not have to deal with the effects of neighboring frequencies, so they are legal.

radios that are 1992 narrowband came with a gold sticker/stamp to indicate they were certified for narrowband use "Gold Certified"
Dec 06, 2015, 12:27 PM
Grumpa Tom
Kmot's Avatar
Quote:
Originally Posted by cyclops2
Is 75 MHZ not legal ?
Quote:
Originally Posted by coriolan
27/53/75 Mhz are still perfectly legal for surface use, don't know what Kmot meant!
Quote:
Originally Posted by frankg
I think what KMOT means is that the 72 & 75mhz frequencies should be checked for channel splash over by a radio technician to see if it meets and is certified with a gold label for continued use on that channel spread.
Quote:
Originally Posted by tsenecal
to paraphrase frankg... and put it in terms i can understand.

prior to 1992, radios were "wideband", after 1992 radios are "narrowband". 75mhz "wideband" are not legal, because they can cause interference on new "narrowband" radios that are using neighboring frequencies. the 27mhz modules/versions do not have to deal with the effects of neighboring frequencies, so they are legal.

radios that are 1992 narrow band came with a gold sticker/stamp to indicate they were certified for narrow band use "Gold Certified"
Correct. Those of us who have been involved in radio control for awhile had the wide band 72 and 75 Mhz radios that were banned from use by the FCC after 1992.

I still have some wide band radios that are now strictly collector items, or candidates for conversion to 2.4Ghz.

Most all my narrow band 72 and 75 Mhz stuff I sold off.


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