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DIY knobby radio?

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Old 11-14-2005, 10:33 PM
  #1  
goldy9955
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Default DIY knobby radio?

Hello, I've been wanting to try a knobby (3channel-1 stick) for awhile. Does anyone know if
there is a DIY kit to convert a standard radio? I saw on e-bay the other day a knob that fits
on top of the gimbal with wires coming out of the knob to the radio internals. I'd like to try
rudder control like that without spending big bucks in case I don't like it. [8D]

Thanks goldy9955
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Old 11-16-2005, 02:09 PM
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The PIPE
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Default RE: DIY knobby radio?

Dear Goldy9955:

The PIPE Here...



an "EXCLUSIVELY knobby flyer" [NEVER dual sticks for me!] from way back in 1977...sadly, these days rudder knobs for a "new" knobby radio are NOT easily available...but I'm planning on "doing my part" in remedying that problem!

I'm slowly getting together the components to use for dimensioning, and design, for an all NEW rudder knob design that will be "broadly" based on the JR knob that the Century Seven knobby Tx used many years ago. A Bourns 3852 pot, with a 1/8 inch diameter knob shaft, would be used as the "heart" of this new design, and as I've assembled ALL my own knobby radios in the past, even the knobs (mostly in maintaining them), I'm quite sure I could design an easily maintainable rudder knob assembly-and I WILL be doing so in the coming months.

Nowadays just about ALL the RCers wanting to have their own knobby radios are going the FCC's Amateur Radio Service route, studying and taking the 35 question [with no more than nine wrong answers to pass] multiple-choice exam for it at a Ham club's testing session (NO morse code required), and getting their Technician class Ham license...and finding old RC knobby radios on the Internet, "stuffing" them with NEW computer RC Tx encoders (the one mentioned at http://mstar2k.com/MicroStar.htm is far and away the MOST popular one to use...I've got TWO of these myself!), and using a 50 MHz RF module (on the 00-09 numbered channels in the USA and Canada)...from ANY of the big three Asian radio makers [Futaba, JR or Sanwa/Airtronics]...and having a GREAT time flying with a knobby radio, with ALL the aerodynamic controls on ONE hand!

The VERY strict "Part 95" FCC rules on what one can do to their OWN RC radio, as far as turning it into a knobby one, make it VERY desirable to just "chuck" the use of 72 MHz, get the Tech Ham license, build a 50 MHz RC transmitter instead, and basically "say goodbye" to the restrictions of FCC's Part 95...which, by the way, you can check out for yourself at http://www.access.gpo.gov/nara/cfr/w...7cfr95_00.html ...as it's even "legal" to MIX brand names of RF deck and Tx encoder on the 50 MHz band, something that CANNOT be done on 72 MHz!

I've been a Ham ever since 1978 (mostly to HAVE the six meter band "mostly" to myself where I fly-but it DOES help in building my own knobbies)...even an AMA District VP or two has one, OR is on the way to getting one, as mine (Andy) wants to get into knobby radios himself...so I imagine HE will soon be studying with a Ham club near him to get a Tech license...and in the Harlingen, TX area, within 50 miles of zip code 78550, at http://www.arrl.org/FandES/field/clu...cation&dist=50 I've even FOUND you a couple of Ham clubs YOU can study with...to get that Tech class Ham license!!!

There ARE a VERY few intact knobby radios available out there on the Internet, that are still on 72 MHz...mostly JR units, AND a few others...that COULD be set up by a place like Radio South for your needs, with new RF decks, and get their gold sticker narrowband certification, but be prepared to spend some cash for one of those...and you WILL very likely have to look HARD for one!!!

I'm just glad I've HAD a Ham license for all these years...and can build and fly with my OWN knobby radios, even these days, thanks to that Ham license, so please think about getting one...it's FREE of charge, and lets you have a knobby RC radio of your own in the easiest way possible !!!

Yours Sincerely,

The PIPE!
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Old 11-19-2005, 06:58 AM
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goldy9955
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Default RE: DIY knobby radio?

Hey Pipe, That's a good idea, coming up with a kit to convert it yourself. Does one need to
be FCC licensed to make such a change to a transmitter?. I'm not sure if that modification would affect RF output characteristics. I have a Futaba 4 channel FM of recent manufacture and
I would also like to install dual rates, I have a slew of old AM radios that I tinker with and for
parts. I don't fly them though. I can solder really well and use fluke meters and can read
schematics. I fly along the Texas Mexican border usually alone. I've read some of your posts
and you're really up on this kind of matters. I would like to know how you're coming along with
your knobs. The one I saw on e-bay looked homemade using a pot contained in a common
radio knob that screwed on the gimbal shaft, heck, I could do that! Thanks goldy9955 [8D]

Should have bought one when I started rc flying in 1978, but the cox 4 channel I bought instead
was 20 bucks cheaper [:@]
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Old 11-19-2005, 07:59 AM
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The PIPE
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Default RE: DIY knobby radio?

It's that "rule 22" in the Personal Radio Service that's the "sticking point"...

Dear Goldy9955:

The PIPE here once again...and from the text of that "rule 22" in the Personal Radio Service regulations...

"Subpart C--Radio Control (R/C) Radio Service

Sec. 95.222 (R/C Rule 22) May I make any changes to my R/C station transmitter?

(a) You must not make or have anyone else make an internal
modification to your R/C transmitter.
(b) Internal modification does not include:
(1) Repair or servicing of an R/C station transmitter (see R/C Rule
21, Sec. 95.221); or
(2) Changing plug-in modules which were certificated as part of your
R/C transmitter.
(c) You must not operate an R/C transmitter which has been modified
by anyone in any way, including modification to operate on unauthorized
frequencies or with illegal power."


Now I'm NOT "really certain" if changing parts of the "user interface"...the things ON the transmitter case that you operate to control the model...might be considered "external" changes, that rule 22 might NOT cover...but compare rule 95.222 to a "somewhat related" rule in the Ham radio regulations. that DOES specifically covers RC use of frequencies on the Amateur Radio Service...

PART 97--AMATEUR RADIO SERVICE--Table of Contents

Subpart C--Special Operations

Sec. 97.215 Telecommand of model craft.

An amateur station transmitting signals to control a model craft may
be operated as follows:
(a) The station identification procedure is not required for
transmissions directed only to the model craft, provided that a label
indicating the station call sign and the station licensee's name and
address is affixed to the station transmitter.
(b) The control signals are not considered codes or ciphers intended
to obscure the meaning of the communication.
(c) The transmitter power must not exceed 1 W."


So, "there you are"...the Hams on 50 MHz, like myself...AND hopefully, soon to include my AMA District VP, Andy Argenio...are NOT bound by a set of such restrictive regulations on what we can do for our RC transmitters ! Andy will soon be starting his studying towards getting a Technician-class Ham license...and YOU might want to seriously consider doing the same, especially if you're good with a soldering iron...and there are even online sites, like what you can find at http://www.qrz.com/testing.html , where you can even PRACTICE taking the 35 question Technican exam...don't forget to check with those two Ham clubs I found for you, to get even more practice with in studying for it!

Andy's first knobby radio, a recently acquired JR Century Seven knobby, had a common failure occur during shipment to him, that those vintage radios from around 1990 have ALWAYS had...a VERY fragile plastic "pot holder" that serves as the rear part of the knob, acts as the rudder pot's mount, and mounts the entire knob onto the hollow joystick shaft.

The plastic "pot holder" part of the rudder knob broke during shipment of the radio to Andy, but THANKFULLY "someone" in the USA came up with a solution, some time ago, to that problem with JR knobby radios...a machined aluminum REPLACEMENT "pot holder", which I've included a photo or two of with this reply. Tony Stillman at Radio South has these readily available for JR knobby box owners, and Andy will be getting his Century Seven sent down VERY soon (hope you got it shipped, Andy!) to Radio South for the repair.

And even though I don't have a JR knobby of my own, I'll be getting one of those "metal pot holders" myself in December from Tony Stillman...it's going to be for the NEW rudder knob project, as a basis for designing the equivalent part for my design.

One of the photos I've included also shows what the JR rudder knob's pot looks like...it SEEMS to be almost the same physical size as the Bourns 3852 pot, and where my design will be based "broadly" on the JR rudder knob, but use the Bourns pot instead, my new rudder knob design will have a readily REPLACEABLE main working part in it.

The prototypes will be used on my soon-to-be-restored Ace Silver Seven knobby radios, one of which you see me using in that photo in my first reply to you in this thread...both of those radios, which I built a quarter century ago, NEED new metal gimbal joysticks placed into them, and I've got those Ace RC joysticks here at home, ready to get new rudder knobs on them...atop lengths of K&S 3/16" OD stainless steel thick wall tubing to act as hollow joystick shafts.

I'll make the prototypes mostly from epoxy, poured into molds I'll make up for the knob barrel, pot holder and other "needed" parts that plastic might ordinarily be used in a production version...a metal barrel with set screw will be in the pot holder section to mount it onto the stainless steel stick shaft, and sheet stainless steel or aluminum will be used for the "stick scissors" that help provide the centering force needed for a rudder knob to operate properly.

During this coming "new year" of 2006 I'll have QUITE a bit of time to sit down at my PC to do the necessary CAD work for a new rudder knob design...as sometime in the spring of next year I'll be getting a left hip replacement installed to match the one in my right hip from five summers ago...and will be AWAY from my day job (recuperating at home) for some 6-to-7 weeks of time. My "original" right hip wore out in 2000, and the very same, fine Boston area hospital that specializes in just this sort of thing-and that did my right hip work "back then" will be doing the left hip as well...heck, I've even got the SAME surgeon doing my left hip as with the right one!

Check out these photos of the "metal pot holder" on the JR rudder knob of a fellow modeler's radio...it's what Andy will be getting for his, VERY soon!

Yours Sincerely,

The PIPE!


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