Change channels with crystal
JLacey7780
I have changed a Ch38 Futaba FM transmitter to Ch60 by changing only the
transmitter crystal.
Before flight I verified the setup using the ground test method (Tx antenna
retracted, at least 75 feet range) and all was OK. I had several flights with
handling just like with the original Ch60 Tx before I got too cute on the
sticks and stalled on takeoff.
DISCLAIMER: Futaba recommends having internal adjustments made to peak the
particular channel but does not give a procedure (and it is probably illegal
for uncertified tweaking). Several usenet messages advised against changing
more than a few channel numbers up or down. But it seems that it CAN work for a
wider change; but make sure to do at least the ground check!!!
Mario Spina
I was just at the radio guru's last night getting a reciver changed
from 46 to 60. I watched him do it and you could really see the size
of the spikes get much bigger as he tuned it to the crystal. The
higer the spikes peaked the better the range would be. I would not
move more than 1 channel up or down without getting retuned.
Mario
bery
JLacey7780 wrote:
>
> I have changed a Ch38 Futaba FM transmitter to Ch60 by changing only the
> transmitter crystal.
>
> Before flight I verified the setup using the ground test method (Tx antenna
> retracted, at least 75 feet range) and all was OK. I had several flights with
> handling just like with the original Ch60 Tx before I got too cute on the
> sticks and stalled on takeoff.
>
> DISCLAIMER: Futaba recommends having internal adjustments made to peak the
> particular channel but does not give a procedure (and it is probably illegal
> for uncertified tweaking). Several usenet messages advised against changing
> more than a few channel numbers up or down. But it seems that it CAN work for a
> wider change; but make sure to do at least the ground check!!!
The matter has been handled several time in this newsgroup.
You just did something illegal if you are in the US but technicaly valid
and harmless and currently done (legally)everywhere else.
The bottom line is that all tuned circuit in a transmitter RF stage are
LC circuits with bandwiths of a couple of Mhz and only the xtal
determines the exact frequency.
All manufacturers tune their RF decks on benches with dummy loads, to
the same specs and in the center of the band .
According to the regulations of the country cristals will be soldered or
socket mounted.
If you look at rf modules by hitec for their 720 serie you will see the
pcb is forseen for both options.
Now there where technically valid reasons for the FCC to make such
rules.
Back then when 72MHz was introduced for rc, Xtals at those frequency
were neither very precise nor very stable and each oscillator had to be
properly tuned to operate reliably and the frequency fine tuned with a
variable capacitor which required a certain level of technical knowledge
and some instruments.
Today xtal manufacuring has made quantum leaps and transistors are well
known and reliable beasties but law stands.
By the way aren't you allowed by the same FCC to swap xtals in 27 MHZ?
Happy landings
Georges
Richard & Diane
I called HiTec today and was told that in other brands you probably can
get away with a couple of channels but not to try it with theirs as they
are built differently so it must be sent back to them to be retuned.
Hmmm.
Grickford
In article <6gf5b0$q...@bgtnsc03.worldnet.att.net>, Richard & Diane
<PugsN...@worldnet.att.net> writes:
>I called HiTec today and was told that in other brands you probably can
>get away with a couple of channels but not to try it with theirs as they
>are built differently so it must be sent back to them to be retuned.
>Hmmm
Hmmm indeed!
In the UK Hitec distribute their whole range of receivers to dealers (don't
know about Txs) WITHOUT crystals and specifically state that they have to be
purchased separately. Does the 'tuning' issue only apply to Transmitters?
Any electronics whiz kids want to comment?
Greg
Joe Baccellieri
I believe that is done in the US as well. When I purchased a Hitec RCD
receiver at the WRAM show the vendor asked me which channel I wanted and
popped the crystal in. I'm pretty sure most dealers do the same thing.
Joe Baccellieri
Grickford wrote in message
<199804080930...@ladder03.news.aol.com>...
Don Hatten
Richard & Diane wrote:
> I called HiTec today and was told that in other brands you probably can
> get away with a couple of channels but not to try it with theirs as they
> are built differently so it must be sent back to them to be retuned.
> Hmmm.
Hmmm is right. If it is this critical that you send the radio back to
get retuned, why make the crystals removable by the customer? Put them
back inside like the old days. I think HiTec may be scamming you.
Having never changed the crystals, this is my opinion.
--
*****************************************
Don Hatten hat...@syix.com
1170 Kenny Dr #1 AMA #SOARDOG
Yuba City, Ca 95991 USHGA #17442
KE6TJG
*****************************************
bery
Richard & Diane wrote:
>
>
> I called HiTec today and was told that in other brands you probably can
> get away with a couple of channels but not to try it with theirs as they
> are built differently so it must be sent back to them to be retuned.
> Hmmm.
Hi,
Hmmm as you said, the last time (6months ago) I opened a hitec flash
I found the rf module to be of the same layout and using the same
components as my 92 vintage aristocraft/hitec/world/kyosho/conrad/polks
challenger 720.
A look at a robbe terratop (futaba (FG ?) packaged for germany ) showed
the electronics in the rf module to be identical ( down to the layout of
parts) except for the connector (more pins).
I use more recent futaba modules in my 720 (non pcm type) with succes
and naturaly opened them to find, guess what, identical parts same
layout .
Now what is true is that in the 720 the xtal is soldered whilst the
others had sockets, and it is easy to be clumsy with a soldering iron
and solder wick/pump if one has not a bit of experience.
Having said this there can be legal problems typical to the US (lawsuits
and so on)linked to this, which hitec are more sensitive to than others,
but regarding the technical explanation I will not write the word I'm
thinking of.
Anyway as you are in the States, I would not bother arguing for a
couple of bucks but I would probably try to get via AMA, SFA, LSF or
whatever modellers association you belong to,to gather evidence and get
FCC to change the rules (good Luck!!).
In the meanwhile if you're not a lone flier midst of nowhere, better
stick to it just for the sake of insurances.
Happy landings
Georges
Ken Battersby
On 8 Apr 1998 09:30:34 GMT, gric...@aol.com (Grickford) wrote:
>In the UK Hitec distribute their whole range of receivers to dealers (don't
>know about Txs) WITHOUT crystals and specifically state that they have to be
>purchased separately. Does the 'tuning' issue only apply to Transmitters?
>
>Any electronics whiz kids want to comment?
>
>Greg
Hi
It has been mentioned before in this NG but here in the UK it is
standard practice for flyers to change crystals in the R/C gear with
no apparent reduction in range. Model stores routinely sell crystals
separately and if you buy a Tx/Rx combo even reputable dealers will
just fit the crystals of your choice.
Even more interesting is that I recently phoned the main JR agents
here in the UK to enquire whether the Tx and Rx crystals have to be
matched pairs when changing frequency. The answer was that it was
perfectly OK to buy Tx and Rx crystals separately as long as they were
on the same spot frequency. No mention was made about the gear having
to be returned to them for re-tuning. Furthermore all that their
instructions with new gear says on the subject is that if the gear is
not supplied with crystals then only genuine JR should be fitted.
Also I have a Sanwa (Airtronics in the USA) manual in front of me and
there is a section entitled "Method of replacing crystals." with NO
mention of returning it for re-tuning.
What gives?? Are you Yanks being conned or are we Brits being given
dangerous info by the R/C trade?? Or does the difference in frequency
between the UK & USA make a difference.
Regards
Ken Battersby
To reply by Email please remove X from <GlobalnetX.co.uk>
Don Hatten
Ken Battersby wrote:
>
> What gives?? Are you Yanks being conned or are we Brits being given
> dangerous info by the R/C trade?? Or does the difference in frequency
> between the UK & USA make a difference.
I think we are being conned but the manufacturers are probably CYA in
our litigious society. Does the UK have a lawyer for every 10
non-lawyers? (Exaggeration-no flames please)
Grickford
Guys,
Taking it one step further, would changing to UK (35 MHz FM) be possible with
US Tx / Rx from say Futaba /JR?
Just new crystals from the UK dealer probably but does anyone know different?
Greg
Joe Willmann
Changing from one 72 Mhz channel to another 72 Mhz channel is one thing.
Changing from 72 or 27 to 36 is an entirely different thing.
Impossible to do safely with just a Xtal change.
In article <199804082009...@ladder01.news.aol.com>,
gric...@aol.com (Grickford) wrote:
)Guys,
)
)Taking it one step further, would changing to UK (35 MHz FM) be possible with
)US Tx / Rx from say Futaba /JR?
)
)Just new crystals from the UK dealer probably but does anyone know different?
)
)Greg
These opinions are my own, not the company I work for.
I apologize for the error in my email address. To email me remove the jnkmail.
Joe Willmann
Trifraug
Grickford wrote:
>
> Guys,
>
> Taking it one step further, would changing to UK (35 MHz FM) be possible with
>
>
That's too big a step. You'd have to replace the coils and/or capacitors
in the tuned circuits as well as the crystal. It's easier and cheaper to
buy the right RF section or module in the first place.
...Trifraug
Trifraug
Ken Battersby wrote:
>
[Snip]
>
> What gives?? Are you Yanks being conned or are we Brits being given
> dangerous info by the R/C trade?? Or does the difference in frequency
> between the UK & USA make a difference.
>
as good as they are today. In the 1980s crystal tolerances began to get
better and better, making such things as frequency-synthesized radios a
practical product (I fly a 1984 Kraft).
...Trifraug
Bill Harris
Subject: "Re: Change channels with crystal"
koko...@globalnetX.co.uk (Ken Battersby) writes (in part):
>Also I have a Sanwa (Airtronics in the USA) manual in front of me and
>there is a section entitled "Method of replacing crystals." with NO
>mention of returning it for re-tuning.
>What gives?? Are you Yanks being conned or are we Brits being given
>dangerous info by the R/C trade?? Or does the difference in frequency
>between the UK & USA make a difference.
Ken,
The Airtronics (USA) Vanguard 4/6 manual specifically states "Do not
change crystals! ...return the transmitter to Airtronics"
(paraphrased). I suspect that this advice may be compliance with an
FCC regulation in the US of A. And may also be stated that way to
protect Airtronics from legal liability-- remember, folks are
lawsuit-crazy here.
But from a practical standpoint, especially with the TX, the crystal
is in a tuned LC circuit and this has to be "tweaked" to the
characteristics of a specific crystal. Or, at least, that is my
non-technician understanding.
--Bill
Jim White
"Joe Baccellieri" <jb...@worldnet.att.net> wrote:
>I believe that is done in the US as well. When I purchased a Hitec RCD
>receiver at the WRAM show the vendor asked me which channel I wanted and
>popped the crystal in. I'm pretty sure most dealers do the same thing.
>
>Joe Baccellieri
>
what you're all missing is the "viewpoint"....
when you plug a different crystal into a receiver, the only observable
external effect is that you've shifted it's "reception" frequency...
the secondary effect is that it may loose sensitivity.... less
range.... primarily YOUR problem....
when you plug a different crystal into a transmitter, there are TWO
observable external effects.... a different radiation frequency AND a
modified frequency spectrum.... the further away from the original
frequency, the more spurious emissions (wider bandwidth), since the
operating point is off the peak of the tuned circuits, EVERYBODY'S
problem... admittably, the output will also drop in radiated power, as
will the spurious emissions, but that's not what's regulated (at least
in a downward direction) but the width of the radiated spectrum is....
this fall off in power is the secondary effect, and again, is YOUR
problem...
Jim White
AMA 2466
WB2WOY
WPMPA/BCF/PFC
Treasure Island, FL
Marty Hammersmith
What is the practical effect with changing crystals? It may not be
ideal,
but as a practical matter with radios costing sometimes less than $150
including receiver,
crystals, batteries, etc, do they really "tune" each radio for each
crystal? If so, why not
mount the crystals inside the radio. My Futaba 6XA crystal plugs in
right on the front panel
and the 127 receiver is the same way. Seems to me, you place your order
and the channel crystal
you select is plugged in. Someone please keep me from doing something
stupid if this is incorrect.
--
Marty Hammersmith
Joe Baccellieri
Jim,
If this is true why does Hitec ship their RX's without the crystal
installed, in fact the package doesn't say which channel the rx was tuned
for. The dealers just pop the crystal in giving you the channel of your
choice. Are you telling me that I will have a less sensitive RX because of
this? If so how can I prevent this from happening other than avoiding Hitec
receivers?
Thanks.
Joe Baccellieri
Jim White wrote in message <352fbb78...@news.supernews.com>...
Ian Maclaughlin
Richard & Diane <PugsN...@worldnet.att.net> wrote:
>I called HiTec today and was told that in other brands you probably can
>get away with a couple of channels but not to try it with theirs as they
>are built differently so it must be sent back to them to be retuned.
>Hmmm.
Hi Richard-
Did the Hitec rep you talked to mention that you can't do it with
their Tx's because they will not sell you the Xtal's? That pretty
much settles the issue of whether you must send it back to them for a
frequency change!
Ian
San Diego
Rod Robbins
I don't know if this is gospel or not, but I was recently told over the
phone by a Hitec technician that their receivers are specifically designed
to be broadbanded so that the user can easily change channels in the field.
In fact, Hitec even sells a pack of four randomly selected reciever
crystals for users of the Prism 7x transmitters equipped with Spectra
module. I don't think they'd be selling these crystal packs if there was
any significant danger in changing receiver channels. According to him,
other manufacturers may or may not have designed their receivers this way.
If not, then those probably should be retuned when moving more than a few
channels.
There's probably no reason to avoid Hitec receivers. In fact, local R/C
folklore has it that their receivers are generally superior to most others
on the market.
Transmitters are a different story, legally and otherwise. (Unless you're
using equipment specifically designed for this, like the Spectra module.)
If my impressions are wrong, someone please correct me...
Thanks,
-- Rod
Joe Baccellieri <jb...@worldnet.att.net> wrote in article
<6gio1e$h...@bgtnsc03.worldnet.att.net>...
Rene
The final frequency plays a mayor role. An average xtal may have a
tolerance of ~20 ppm (parts / million). On a 35 MHz system even a
"worst case" xtal is still (usually...) close enough to the desired
frequency. At 72 Mhz, the effect of the absolute tolerance is more
than twice as bad - possibly giving unreliable results. This makes it
advisably to align it after an xtal change.
Note that the channel separation on 72 MHz is *not* doubled.
When mobile radios were still xtal driven (note that all RF equipment
is now PLL except most of R/C :-( ), the VHF models absolutely
needed the xtals to be tuned finely to make the RX / TX sections work
on the desired channel, while UHF radios needed tuning + high priced
low tolerance xtals + temp compensation...
On Wed, 08 Apr 1998 18:04:43 GMT, koko...@globalnetX.co.uk (Ken
Battersby) wrote (may be only partially quoted):
>
>Hi
>
>It has been mentioned before in this NG but here in the UK it is
>standard practice for flyers to change crystals in the R/C gear with
>no apparent reduction in range. Model stores routinely sell crystals
>separately and if you buy a Tx/Rx combo even reputable dealers will
>just fit the crystals of your choice.
>
>Even more interesting is that I recently phoned the main JR agents
>here in the UK to enquire whether the Tx and Rx crystals have to be
>matched pairs when changing frequency. The answer was that it was
>perfectly OK to buy Tx and Rx crystals separately as long as they were
>on the same spot frequency. No mention was made about the gear having
>to be returned to them for re-tuning. Furthermore all that their
>instructions with new gear says on the subject is that if the gear is
>not supplied with crystals then only genuine JR should be fitted.
>Also I have a Sanwa (Airtronics in the USA) manual in front of me and
>there is a section entitled "Method of replacing crystals." with NO
>mention of returning it for re-tuning.
>
>What gives?? Are you Yanks being conned or are we Brits being given
>dangerous info by the R/C trade?? Or does the difference in frequency
>between the UK & USA make a difference.
>
>Regards
>
>
>
>Ken Battersby
>To reply by Email please remove X from <GlobalnetX.co.uk>
-Rene-
Mark Trible
Jim, if this is true tell me how Hitec and Futaba can sell transmitters that
have modules which allow you to select any channel you want?
Mark
Jim White
"Joe Baccellieri" <jb...@worldnet.att.net> wrote:
>Jim,
>
>If this is true why does Hitec ship their RX's without the crystal
>installed, in fact the package doesn't say which channel the rx was tuned
>for. The dealers just pop the crystal in giving you the channel of your
>choice. Are you telling me that I will have a less sensitive RX because of
>this? If so how can I prevent this from happening other than avoiding Hitec
>receivers?
>
>Thanks.
>
>Joe Baccellieri
I can't say for certain, but what HiTec is PROBABLY doing on RCVRS
(only) is using a low Q broadly tuned front end (or a complicated
stagger-tuned parallell filter - though that would not square with
their low price) and tuning it to the center of the band.... you may
see a lower sensitivity (and range) at the ends of the band, but not
of any significance....
Jim White
Mark Trible <do...@usfarm.net> wrote:
>
>Jim, if this is true tell me how Hitec and Futaba can sell transmitters that
>have modules which allow you to select any channel you want?
>
>Mark
the high price of those modules allows some pretty fancy circuitry....
Jim White
Marty Hammersmith <bal...@worldnet.att.net> wrote:
> What is the practical effect with changing crystals? It may not be
>ideal,
>but as a practical matter with radios costing sometimes less than $150
>including receiver,
>crystals, batteries, etc, do they really "tune" each radio for each
>crystal? If so, why not
>mount the crystals inside the radio. My Futaba 6XA crystal plugs in
>right on the front panel
>and the 127 receiver is the same way. Seems to me, you place your order
>and the channel crystal
>you select is plugged in. Someone please keep me from doing something
>stupid if this is incorrect.
I think the intention is that a guy could get, say three crystals....
the original, and one step up and one step down.... and avoid
conflicts at the field while staying within the tuning range of his
equipment...
Kevin Kline
I think the bottom line here is we, as average modelers do not know the
specifics of how the radios go about deriving the Tx freq. Since we can
take three crystals and synthesize from these any channel we use, we can
never be sure how the RF section of our radios work anymore. I say send
it to the manufacturer or authorized service center and let them do it.
Cheaper then a new plane. Besides, then you have someone else to blame
for the pile of rubble next to the runway.
K. Kline
Bill Harris wrote:
>
> Subject: "Re: Change channels with crystal"
> koko...@globalnetX.co.uk (Ken Battersby) writes (in part):
>
> >Also I have a Sanwa (Airtronics in the USA) manual in front of me and
> >there is a section entitled "Method of replacing crystals." with NO
> >mention of returning it for re-tuning.
>
> >What gives?? Are you Yanks being conned or are we Brits being given
> >dangerous info by the R/C trade?? Or does the difference in frequency
> >between the UK & USA make a difference.
>
Mike Mayberry
Let me set the record straight as far as Hitec is concerned. Changing crystals
in transmitters is illegal unless the transmitter is re-tuned to the new
crystal. You don't have to be a licensed technician to change it legally you
just have to be abel to re-tune it. Since most of us don't have the necessary
equipment to do so, you would need to have a technician do it. Hitec does not
make our transmitter crystals available to the consumer separately. They must
be purchased through an authorized service center when changing frequencys. I
know, I know.. other companies sell transmitter crystals but it is still not
legal to just plug them in.
As far as receivers go... that is an entirely different story. Hitec/RCD
receivers are centerline tuned. You can simply plug in any channel crystal on
the same band and their will be only a 2% variance at either end. As far as the
other manufactures equipment I cannot accurately comment on them. You may want
to contact them and ask what their policy is. Hitec/RCD receivers are sold
without crystals, just plug in the proper channel and range check. We recommend
range checking with the motor running. You must get a minimum of 75 ft with the
antenna collapsed but 150 ft is not uncommon.
If anyone has any questions or comments about Hitec/RCD products you can visit
our website @ http://www.hitecrcd.com or E-mail me @
mailto:mayb...@hitecrcd.com We are here to help!
Sincerely,
Mike Mayberry
Consumer Relations
Hitec RCD Inc.
DMorris512
Rod Robbins wrote:
>I don't know if this is gospel or not, but I was recently told over the
>phone by a Hitec technician that their receivers are specifically designed
>to be broadbanded so that the user can easily change channels in the >field.
It is probably true. Quoting from my FMA Tetra manual:
"So if you have a Futaba and a JR transmitter with you at the field on
different R/C channels, and one channel is already in use, you can simply plug
in the correct receiver crystal, change the settings of the dip switches and
you're ready to fly.".
The dip switches set the pulse direction.
Mine was shipped from FMA with the xtal in a separate bag for me to plug in.
They are broadband. As for chopping the antenna, no problem. It will not detune
the receiver if you do not go shorter than 18 inches. I am using the control
rod on a 5 ounce glider as most of the antenna. Total length 20 inches. Range
is of course decreased, but I would need a telescope if I flew to max.
Dan
Carmack
Why is it impossibe??????????
Peter Goldsmith as far as I know just changes his TX module when he goes to the USA
to fly???
Though I could be wrong
Carmack
Joe Willmann wrote:
> Changing from one 72 Mhz channel to another 72 Mhz channel is one thing.
> Changing from 72 or 27 to 36 is an entirely different thing.
>
> Impossible to do safely with just a Xtal change.
>
> In article <199804082009...@ladder01.news.aol.com>,
> gric...@aol.com (Grickford) wrote:
> )Guys,
> )
> )Taking it one step further, would changing to UK (35 MHz FM) be possible with
> )US Tx / Rx from say Futaba /JR?
> )
> )Just new crystals from the UK dealer probably but does anyone know different?
> )
> )Greg
>
> These opinions are my own, not the company I work for.
> I apologize for the error in my email address. To email me remove the jnkmail.
> Joe Willmann
Kevin Kline
Carmack wrote:
>
> Why is it impossibe??????????
Because when you change bands, (72 to 36) you also have to chamge the
other components in the RF deck. Reason being, the crystal isn't the
only part whose value is based on the desired frequency. Capacitors,
coils and even some resistors would have to be changed out when
switching bands. OK, so your system is all digital with IC chips.
Guess what those chips contain? Caps, resistors and transistors. All
desigend to operate within certain limits of which frequency is the
number one spec after voltage.
>
> Peter Goldsmith as far as I know just changes his TX module when he goes to the USA
> to fly???
If he changes bands he must be changing the RF module. That is the only
SAFE way he could do it short of identical radios.
K. Kline
Jim White
that's a MODULE change, not a CRYSTAL change....
Carmack <q962...@helios.usq.edu.au> wrote:
>Why is it impossibe??????????
>
>Peter Goldsmith as far as I know just changes his TX module when he goes to the USA
>to fly???
>
>Though I could be wrong
>Carmack
>
>Joe Willmann wrote:
>
>> Changing from one 72 Mhz channel to another 72 Mhz channel is one thing.
>> Changing from 72 or 27 to 36 is an entirely different thing.
>>
>> Impossible to do safely with just a Xtal change.
>>
>> In article <199804082009...@ladder01.news.aol.com>,
>> gric...@aol.com (Grickford) wrote:
>> )Guys,
>> )
>> )Taking it one step further, would changing to UK (35 MHz FM) be possible with
>> )US Tx / Rx from say Futaba /JR?
>> )
>> )Just new crystals from the UK dealer probably but does anyone know different?
>> )
>> )Greg
>>
>> These opinions are my own, not the company I work for.
>> I apologize for the error in my email address. To email me remove the jnkmail.
>> Joe Willmann
Jim White
DMorris512
Kevin Kline wrote:
>Carmack wrote:
>>
>> Why is it impossibe??????????
>Because when you change bands, (72 to 36) you also have to chamge the
>other components in the RF deck. Reason being, the crystal isn't the
>only part whose value is based on the desired frequency. Capacitors,
>coils and even some resistors would have to be changed out when
>switching bands. OK, so your system is all digital with IC chips.
>Guess what those chips contain? Caps, resistors and transistors. All
>desigend to operate within certain limits of which frequency is the
>number one spec after voltage.
>
>> Peter Goldsmith as far as I know just changes his TX module when he goes to
the USA
>> to fly???
>If he changes bands he must be changing the RF module. That is the only
>SAFE way he could do it short of identical radios.
>K. Kline
True, he must be changing RF modules. But what was that other stuff about? The
digital circuits do not operate on the transmit frequency. They have their own
clock which is much lower frequency
Dan.
Kevin Kline
I've not delved in to what the current RF decks look like on our
radios. So I was simply covering all bases. I would have to suspect
the radios that synthesize the freq do so digitally. I do know there
are some radios (again, not R/C) out there that do all freq tuning
digitally. I get this from my customers who happen to be on the cutting
edge of communication engineering.
K. Kline
Jim White
dmorr...@aol.com (DMorris512) wrote:
>
>True, he must be changing RF modules. But what was that other stuff about? The
>digital circuits do not operate on the transmit frequency. They have their own
>clock which is much lower frequency
>
>Dan.
I'll jump in and answer this.... it's really quite simple... when I go
flying on the weekend, I take, at the minimum, two planes. One is on
channel 15 in the 72 mhz band, the other is on channel 02, which is in
the 50 mhz band.... I have one transmitter, a Futaba 8U.... the model
names I programmed in have a suffix of 15 or 02.... I insert the
correct RF module into the back of the transmitter and fly....
Trifraug
DMorris512 wrote:
>
[Snip]
>
> True, he must be changing RF modules. But what was that other stuff about? The
> digital circuits do not operate on the transmit frequency. They have their own
> clock which is much lower frequency
>
> Dan.
The frequency-synthesized radios, such as my Kraft, divide the output
frequency digitally and compare it with a lower-frequency internal
crystal to generate a correction voltage. Changing channels actually
changes the division ratio. It's a bit more complex than that, but
that's the general principle.
...Trifraug
DMorris512
Trifraug wrote:
>The frequency-synthesized radios, such as my Kraft, divide the output
>frequency digitally and compare it with a lower-frequency internal
>crystal to generate a correction voltage. Changing channels actually
>changes the division ratio. It's a bit more complex than that, but
>that's the general principle.
You are quite right. However, Kevin Kline did not mention synthesizers and was
talking about standard radios. The computer radios have digital circuits which
operate at a frequency which remains fixed and does not depend on the transmit
frequency.
Dan