<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1">
<title></title>
</head>
<body text="#000000" bgcolor="#ffffff">
I would love to hear from an authorized Futaba repair center on this
issue. I am sure there are alot of people out there changing crystals.
I am in the process of changing frequencies myself on all my planes and
would like an official answer. There are plenty of other radios that
have no module and provide access to crystals for changing. Even some
of the older Futaba radios provide access to the crystal from the
exterior of the radio. I doubt if they were woried about someone
changing frequencies they would have made it that accesible. My guess
is the manufacturers have seen an opportunity to make even more money
by telling people that have purchased the more expensive radios that in
order for them to change their frequency that they have to buy a $50.00
module in lieu of a $10.00 crystal. <br>
<br>
John Pavlick wrote:<br>
<blockquote type="cite"
cite="midNHBBKICNKLHCPALOKCBOGEIJCLAA.jpavlick@idseng.com">
<pre wrap="">Scott,
Yeah, what Ed said... Just change the RF module in the transmitter and get
a new crystal for the receiver. I think the RF module for a 9c is about
$50.00. Not too bad. You are not supposed to change just the crystal in the
transmitter - that's why we have modules. Changing just a crystal (in the
transmitter) requires re-tuning otherwise you might interfere with someone
else. The module is tuned to the chosen frequency and sealed up. Nothing
wrong with having a few modules either. The synthesized RF module is another
alternative. Like Ed said it is tuned to a stable frequency, then a PLL
(Phase Locked loop) circuit generates the chosen carrier frequency. Also
acceptable and legal. Bottom line: change the transmitter module and the
receiver crystal and you'll be within FCC regulations and safe from any
Homeland Security issues too.
John Pavlick
<a class="moz-txt-link-freetext" href="http://www.idseng.com">http://www.idseng.com</a>
</pre>
<blockquote type="cite">
<pre wrap="">-----Original Message-----
From: <a class="moz-txt-link-abbreviated" href="mailto:discussion-request@nsrca.org">discussion-request@nsrca.org</a>
[<a class="moz-txt-link-freetext" href="mailto:discussion-request@nsrca.org">mailto:discussion-request@nsrca.org</a>]On Behalf Of Ed Alt
Sent: Wednesday, June 29, 2005 11:52 PM
To: <a class="moz-txt-link-abbreviated" href="mailto:discussion@nsrca.org">discussion@nsrca.org</a>
Subject: Re: Changing Frequencies.....danger??
This is quite possibly incorrect. Depending on how it has been
designed, it
may not legal or advisable to change crystals in a module unless
you are FCC
certified to do so and have the equipment to assure that the transmitted
energy is within spec. Think of it: the reason we have modules
is because
you're suppose to swap the module, not the crystal. Ofcourse it
"works" to
swap a crystal. All this proves is that you didn't break anything
important when you broke the potting seal that you usually find on the
crystal. This potting seal is there to tell the bench technician whether
you've been tampering with the module.
When you swap crystals, you run the risk of transmitting with
less than peak
power on your channel, thus wasting energy that would normally
radiate out
of the antenna and instead heating the module's components more
than normal.
You also run the risk of transmittnig above legal levels of RF energy
elsewhere, in other words, you may contribute to interference on other
channels. You have to realize that you never get a completely
clean signal
just on your channel when you operate your transmitter. Part of the
procedure of producing an RF module includes tuning, or more correctly,
aligning the tuned circuits in the module to the center frequency
you want
to transmit on and bringing the unwanted byproducts down to acceptable
levels. When you swap crystals on your own, you have undone this
work, at
least a little bit, maybe by an unacceptable amount. Depends on
how broadly
tuned the module is designed to be in the first place.
Why does a synthesised RF module work? It's designed with a tightly
controlled feedback loop to lock onto the desired frequency and maintain
other unwanted RF energy well below specified levels. Why does
it work to
swap crystals in receivers? Because the front ends are broadly
enough tuned
to allow energy to be received efficiently within a specified
pass band, in
our case usually much of the 72 mhz band. The fine tuning, i.e.
what makes
our receivers highly selective to the channel we want is mostly
accomplished
by circuitry that is past the stage of the front end.
Ed
</pre>
</blockquote>
<pre wrap=""><!---->--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.323 / Virus Database: 267.8.7/34 - Release Date: 6/29/05
=================================================
To access the email archives for this list, go to
<a class="moz-txt-link-freetext" href="http://lists.f3a.us/pipermail/nsrca-discussion/">http://lists.f3a.us/pipermail/nsrca-discussion/</a>
To be removed from this list, go to <a class="moz-txt-link-freetext" href="http://www.nsrca.org/discussionA.htm">http://www.nsrca.org/discussionA.htm</a>
and follow the instructions.
List members email returned for mailbox full will be removed from the list.
</pre>
</blockquote>
</body>
</html>