Grampaw

Reading all this has relit an urge I had some time back. Thanks guys. As they say "I needed that!" You see, I have an Ace Olympic V Single Stick on 27 gathering dust. I also have a gutted Heathkit "Slim Transmitter" case. I always liked it as it fit in the palm of my left hand nicely and the Throttle slide switch fell under the third finger of my hand. My right hand worked the stick and knob. The Ace was a square type of case, which I never really got comfortable with. So, I had planned to someday gut the Ace and install all the parts in the Heath Tx case and continue using it. 27 is still legal, except at sanctioned AMA events where 72 is the numbers. And it is allowed at our field as we don't have any sanctioned events out there. Fly what you bring, as long as it's legal. Oh, and for the record, I flew my Heathkit on 27 from the day I built it up until the late 90's and never had a glitch, or any interference. Guess I'll call it a Heath/Ace V SS. That ought to get some questions. I still remember my Marine Corps Service from 57 years ago, but can't come up with my old
FCC number. Time flys.

iflyj3

My Feedback: (7)

"27 is still legal, except at sanctioned AMA events where 72 is the numbers."

OH contrare, 27 is legal period. If it is not allowed, that is a local rule and not AMA or FCC.

BobHH

My Feedback: (18)

Dan is correct. The Mid-South VRCS Fly-In is an AMA sanctioned event and about 50% of the radios used last year were on 27mhz. 27 is still a legal frequency for the AMA.


Bob Harris
Early RC Models

jimcork1

My Feedback: (4)

Fly 27 Mhz and have fun.. I'm back,, even katrina didn't keep me from saving my 27 MHz radio. But I will consider the futuba 27 mh rec. and 3 wire servor. Our home is rebuild and we are sleeping inside not ourside as the last 6 months. The news doesn't give justice to the destruction and politicians that should be still in the kitchen, vs. leading a state rebuild. Jim

John Schall

I own a lot of 27 mhz equipment, a lot of it is 72 mhz equip converted to 27, because it couldn't be narrow banded. Receivers are easy to convert, tx a little harder. I use them mostly in sailboats, but I plan to use a Citizen Ship DPT-3 in a plane soon.

fritzke

My Feedback: (1)

This is the only 27 mhz radio available today that could really be used to fly:
http://www3.towerhobbies.com/cgi-bin...I=LXSNP1**&P=0
You would have to make the left sticks ratchet for the throttle
(mode 2 anyway)
Dave

iflyj3

My Feedback: (7)

Looking at the web site they keep saying surface. This to me means it has limited range and may not be suitable for aircraft.

In this day and age with versatility of spread spectrum radios, I don't know why anyone would buy a 27 or 72 MHz system.

The 27 MHz ones in use are primarily old 60's vintage and are used in the vintage movement, even though it is not required.
I built my own single channel transmitters on 2.4 GHz so I would not have to use the old 27/72 stuff.

72 MHz came about 1967 and that almost did in 27 MHz because of the CB interference. 2006 spread spectrum came and it has done in 72 MHz.

John Schall

I understand you young guys not wanting to mess with stone age equipment. I am 63, so it isn't too stone age for me. Vacuum tube and superregerative, now that's stone age. I started at 13yrs old in ,66, so 27 mhz was the norm then, 72 was beginning to come out a few years later. Everything was fine until the CB craze of ,76 began. It went strong for about 2 yrs then slowly faded away. Then in ,78 the new rules for the 72mhz came out. I began converting 72 mhz equip to 27mhz because some of it would never pass. A lot of guys sold their old 72 radios in swap shops, so I picked a lot of it up cheap and converted it to 27 mhz. A receiver is easy, most (except Heathkit) , just rewind the antenna coil for 27. You usually have to remove the old wire, and rewind with finer wire, about twice as many turns,and sometimes the capacitor across it to get it to resonate at 27mhz. Always the crystal must be replaced. Most used a 36 mhz oscillator, so often it would work with no other changes. If not, adding more capacitance across the osc coil will work. Re-tune antenna coil. A grid dip oscillator is helpful.
Transmitters are harder, so I will only cover Kraft from ,73 to about ,80. Rewind osc coil with #26 or smaller wire, 11 turns. Replace capacitor across it with 68pf. Use a 22pf cap to couple to next stage, 220 ohm resistor from buffer stage base to ground. Rewind buffer tank coil to 10 turns, tap 3t from modulator end. Capacitor across tank coil is also 68pf. Another 68pf to couple to final stage, 100Ohm base to ground. Final transistor should be changed to an RCA 40081. A 2N2219-A is reasonable substitute. A 68pf cap from the collector to ground. From collector to the first (13 turns) coil, A 150pf cap,from there to a 220pf cap to ground, from coil end of 220pf cap another coil, 10 turns. Both of these coils use the same coil form, so you will have to scrounge for a 4th coil form and slug. From the other end of 2nd coil, a 47pf cap to ground, and a wire to the antenna. The first coil is the tuning coil, the 2nd coil is the loading coil for the antenna. Adjust the slug of the tuning coil for peak output, with field strength meter. If total current drain is 100ma to 90ma, your done! if less or more, change the loading coil slug adjustment and then re-tune the tuning slug. they interact, so the loading coil must be changed, and then the tuning coil re-tuned to peak output.
I don't expect more than 1 or 2 people to go thru all this crap, but if it's useful to somebody, It's worth my trouble to write it.

iflyj3

My Feedback: (7)

Hi John,

I don't quite meet your description of a young guy as I am 73+. I started flying RC in 1962 with superreg and home built transmitters of which I still have two of them. I got my ham ticket in 1967 so I could get away from the CB craze on 27 MHz. I started with 2.4 GHz in 2006 and still flew some some on 50/53 MHz until abut last year. I am all 2.4 now and don't want to go back.

I do appreciate your description on how you did the conversion from 72 to 27.

kmeyers

John Schall wow, thank you for the good read.

smallrc

I enjoyed reading your 72 to 27 conversion for Kraft. Several years ago I did a similar conversion to 53 MHz on a Kraft tx module. I didn't document it, however, and would have to re-engineer it to do it again. Finding the crystal might be a challenge these days, especially for 53.