Hayes

My Feedback: (13)

Hi Guys,

I was wondering what the best way to test my Tx & Rx frequency
strength. (Other then a range check)

dirtybird

My Feedback: (5)

I assume you mean signal strength.
Radio Shack used to sell a signal strength meter. You might be able to find one if you look for it. Try a google search.
Since the signal strength depends on many things I don't know what it would tell you if you don't really know what you are doing.
Such a meter is usefull an a fixed antenna but almost useless on a hand held unit.

Whirley Bird

My Feedback: (1)

What you need is a watt meter that will measure low power levels of 1 watt and lower.
But to measure this you need to connect direct to the transmitter.
If your not a ham or certified I don't think your allowed to poke around inside the box.
Radio shack sells a cheap field strength meter and that will do better then a range check because it will show what transmitter is putting out a stronger signal.
As a ham I built my own watt meter and have friends that work in large electronic firms and I had all my gear tuned and peaked.
One of my 3/4 watt transmitters was putting out less then 1/4 watt.
Try to locate a local electronic facility in your area.
Futaba will NOT peak your TX for the Max 3/4 watt.

Hayes

My Feedback: (13)

I phrased that wrong, I am looking to test signal strength and
receiver's sensitivity.
What I have done is put a base loaded antenna on my Rx and a
base loaded on my Tx. When they had the stock antenna's they
range check at 150 feet, now they only go to 100 feet.
(Is that ok or not)

Whirley Bird

My Feedback: (1)

First
You cannot change the antenna on the TX.
Against FCC regs
Second when your changing antennas they have to be resonate for the frequency that your on.
You did not say what type of antenna you used but if their not designed for the band your on they wont work.
Also if you change the RX antenna for better reception you need to retune the receiver.
Base loaded coil antennas are not that efficient and if you look around at ham radio antennas on cars the coil is center loaded so the current stays at the bottom and voltage at the top.
Have someone who is qualified to retune your TX and RX and you'll be OK.
If you played with any adjustments inside the TX or RX then you don't know what one you messed up.
You could have peaked the TX and detuned the RX or vice versa.
You need instruments and know what adjustments to turn.

Hayes

My Feedback: (13)

OK,

I will see if I can get someone to take a look at my Tx & Rx.
If you cannot change antennas on your Tx why do they put this stuff up for sale. Here is the link to the antenna I put on.

http://www.hobby-lobby.com/antennas.htm

Thanks for the help!!!!

Ladyflyer

My Feedback: (2)

Hello Hayes ,
Welcome to the very gray area of the unlicensed RC transmitter.
The antenna swap you mention often yields less than desireable results. When an antenna is electrically shortened the tuning becomes more critical. In your case the transmitter should have the out put circuit rematched to the new antenna.
Like Whirley Bird said it is probably illegal . It is a gray area and I doubt any problems once you retune. You may find however the original antenna provided for more range.
For the most part the rule makers are concerned with you extending you range beyond the design intent. If your range (ERP) is diminished it is of little concern to them.
The main thrust of rule making is eliminating interference ,especially to licensed primary frequency users.


In a nutshell ,get it tuned and make sure the range is sufficient as it may not be as great as it was .

Tippie

Ditto to what Ladyflyer says. you need to check the SWR (standing wave ratio) with a (ta dah)"SWR Meter" and tune the antenna to the output. Since you don't change frequency on the transmitter as a HF radio does, once the swr is set there is no need to retune. But since the antenna is direct coupled to the transmitter it will require a few more tools to do it. Not something a novice will be able to do.

Hayes

My Feedback: (13)

I just had a thought,,,,
I did the range check with the stock antenna down
and with the power stik antenna you can not extend
it so something is not right....

Whirley Bird

My Feedback: (1)

OK Marc,
I see your going with a duck antenna.Well with a short stick on the RX you have less capture area.
Another member and I were talking about this last night.
Since I can't contact him I left his name out put i'm posting the info he sent me.
Read below==================================

As for a "Rubber Duck" antenna, what a coincidence - I just read a response from AnnMarie Cross regarding this matter:
"Note, in the US, unless your "rubber ducky" is produced by or certified with the transmitter by the manufacturer, it is against FCC regulation to use and is voiding your AMA insurance as well as your club/site's insurance if any."
This has to do directly with regulation 95.222:
"95.222 (R/C Rule 22) May I make any changes to my R/C station transmitter?
(a) You must not make or have any-one 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, 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. (See R/C Rules 9 and 10, 95.209 and 95.210.)
{48 FR 24894, June 3, 1983, as amended at 63 FR 36610, July 7, 1998}
EFFECTIVE DATE NOTE: At 63 FR 36610, July 7, 1998, 95.222 was amended in paragraph (b)(2) by removing the term ‘‘type accepted’’ and adding in its place ‘‘certificated’’, effective Oct. 5, 1998."
Having said/read all that, it would seem we can't legally change the antenna the way you propose, even though some people do (I wish we could). Most people drive above the speed limit too, but that doesn't make it legal.
+++++++++++++++++++++++++++++++++++++++++++++++
Can you tell me how your feeding that duck antenna?
Also I don't think you have a problem.
You went to a short antenna on both the RX and TX so your range test will be less.
Put the stock antenna back on both units and set the plane on the hood of your car.
You will get 200 feet or better. I built up a pre amp for my RX and converted the antenna to a dipole.
That gives me more capture area and the pre amp will boost up a weak signal.
I haven't tried it as of now but I have to be careful because if the RX is to sensitive it just may pick up unwanted signals from another source.
It sure would be nice if the manufactures redesigned a new receiver and had a roofing crystal that would get rig of a lot of crud but keep the signal you want.
They can't kill me for experimenting with the RX so what the TX lacks I can make up for it with a good receiver

Hayes

My Feedback: (13)

I think I am going to remove the power stick antenna from my TX
and reinstall the stock one and check it with the base load on
the RX and go from there.....

Thanks alot!!!!!!

strato911

That was me.

Here's a link to the FCC's FTP server with the PDF file in question. Check out the section "Subpart C" - it starts on Page 23.
http://ftp.fcc.gov/Bureaus/Engineeri...98/47cfr95.pdf

They sell those antennas because it's another source of income, and most RC pilots don't know they are breaking the law when they use them. Many provinces and states passed laws saying radar detectors are illegal to use, but they are legal to buy. Do you see the similarity?

Hayes

My Feedback: (13)

I get what you are saying and I really like your quote.

(I try to learn from other people's mistakes...
I won't live long enough to make them all myself.)

But it really aggravates me that I find this out after
the fact. The company needs to put a foot note with there add!!!

strato911

I agree. But then they couldn't sell as many.

Since the FCC regulation 95.222 only prohibits internal modification to your R/C transmitter, it may be legal to change antennas which are connected to the outside of the case. I haven't read the entire document...

Unfortunately, most TX's have the antenna screwed onto a post inside the case.

Hayes

My Feedback: (13)

I love this statement,
(Kavan antenna: Same long range as your present long transmitter antenna.)
That's not true, from the problems I'm having....

strato911

How were you holding the transmitter? On another thread I read a couple months ago, it was explained that this style of antenna has a more focused radiation pattern out the tip. I don't have the means to verify this, but if that statement is correct, then pointing the antenna directly at the plane is the way to go. Opposite of the original antenna.

Hayes

My Feedback: (13)

I pointed it at the heli, I pointed it up and down.
The stock antenna had more range with it clasped, than
the power stick.....

Here is the link to the article..

http://www.bergent.net/antenna_field_test.html

Lynx

All these conversations about boosting TX power modifying antenna's etc.. etc.. seem a little run down after a while, especially considering what's more important is how much of the signal actually gets to the receiver. It'd be easier to measure what the strength of received signal from the receiver was for signal strength tests while moving the transmitter around and finding out where/if there were dips or hits in the signal strength.
Range tests are a crude way of doing this. Anyone know of any solutions like this? Or ways of measuring the signal strength in a common receiver?

KG4AWV

Get rid of that base loaded TX antenna. I have personaly expericed radio interference from someone using one. That person was 5 or 6 chanel above me and was still causing problems. And speaking from a HAM Radio Operator point, a base loaded TX antenas DO NOT radiate RF like a full lenght antenna. As far as checking the RX antena. You really need an O-scope to check out the receiver's sensitivity.

Ladyflyer

My Feedback: (2)

Base loaded antennae are about the least efficient of the lot. The tuning I suggested previously is VERY important . There is no way an antenna shortend to the degree you are using can present the proper load other than real dumb luck .
You can expect a lot less range than the original and you are still very much in a gray area legally.
If you are venturing to the gray area it is best to optimize your chances for success. The first time a model goes in from "interference" while you are using the grey antenna you can expect to take some heat.

I can't tell you it is an illegal set up . One FCC rep will say yes,it is the next may say no it is perfectly legal .
I will again say ,expect less range (a little less if tuned a LOT less if not.

Field strength readings at ranges less than 100 feet are almost useless . You will need good stuff to do the job right.

Try Pete Waters or Radio South . They will also be in a better position to confirm the legality.

BTW ;

The Duckie from Smiley Antenna Co is about the best one I have seen . High quality North American made too !