Jump to content
Acetronics

Signal Strenght Meter 2

Recommended Posts

Hi, Every body

As we can find the 455 khz RX signal on the "signal" pin of the Batt connector ...

May be a small instrument to finely tune our RXs could be engineered ... Also to be used to verify "on the field" the transmission quality and usable range.

Alain

Share this post


Link to post
Share on other sites

That is interesting -- Which Rx models have the IF signal on the battery connector?

I've been using the RSSI pin that is found on some demod IC's inside the Rx. That requires soldering to some tiny IC pins.

Share this post


Link to post
Share on other sites

Hi, Mr Cam

To my knowledge Graupner/JR, Futaba and Hitec offer such a feature ... may be levels are different, but always reflecting good tuning ... or correct signal.

It's intended to tune the receivers at factory without having to use a clamp !!!

it's also really easy to test that pin on other RX's w/ a basic scope ... ( mine is just a Hameg 2x20 Mhz !!! )

Alain

Edited by Acetronics

Share this post


Link to post
Share on other sites

That is odd. None of my USA sold Rx's have the IF output on the battery connector. I have an assortment of JR's, Hitec, and Futaba. Perhaps it is a feature of European sold Rx's -- which rx models have you checked for this?

Share this post


Link to post
Share on other sites

Hi, Mr Cam

All my Graupner RX's for 20 yrs ( MC18, MC20, C16, C17, C19 ); Recently 4 Hitec Supreme HFD 07 RA and Futaba R 118 and 138 ...

Plus some club friend's from Multiplex.

Note Graupner need maximum sensitivy from scope ...

Alain

Share this post


Link to post
Share on other sites

It would be great to see this feature on the Rx's I have (could be adapted for a painless RSSI). I wonder if there are any 72MHz (USA) products that have it?

I don't have a Futaba R138, but it is available in the USA on 72Mhz. So, perhaps a forum member can stick a scope on theirs and see if the IF image shows up on the battery connector's sig pin. What is odd is that is the same pin used for the R/C ch-8's PWM signal.

Share this post


Link to post
Share on other sites

The PICS !!!

Tx OFF ...

post-6-1136032941_thumb.jpg

Edited by Acetronics

Share this post


Link to post
Share on other sites

The PICS !!!

a Tx, a Rx ( Graupner C16 ) a Batt, a Scope ... that's all !!!

Alain

post-6-1136033025_thumb.jpg

Edited by Acetronics

Share this post


Link to post
Share on other sites

That is very cool. If there are any USA R/C Rx's that have that feature then it would be great to start a list. So far, I can't contribute.

Share this post


Link to post
Share on other sites
What is odd is that is the same pin used for the R/C ch-8's PWM signal.

Weird...

What seems strange to me is that the battery connector is often also used for a channel just as you said... at least it's the case on all those I have!

Or for some Futaba receivers it can be DSC as well, which is nothing else than the baseband signal...

Have you tested what levels you get at a common R/C range, let's say 300m?

I have an old 72MHz R129DP, battery connector is shared with CH9 and there is one more connector for DSC.

Edited by Kilrah

Share this post


Link to post
Share on other sites
Or for some Futaba receivers it can be DSC as well, which is nothing else than the baseband signal...

The battery connector on some of my 72Mhz JR's is the DSC input as well.

Have you tested what levels you get at a common R/C range, let's say 300m?

Yup, that would be an interesting test, even if performed at 10 meters from the Tx (with Tx antenna collapsed).

Share this post


Link to post
Share on other sites

Hi Mr Cam

:) Wish you a Happy New Year !!!

To trim receivers, I use, instead of the Tx antenna, a 6v 50mA lamp in series with a 47 pF capacitor. ( connected between ant.base and batt - or Tx ground as a dummy load )

That gives me the weakest possible Tx signal to have the best trimming with emitter placed 10 - 20 meters away.

To control practical range, the test can be done W/Antenna at full length and receiver, batt, and tester in the hand. A little walkaround is always good for health. ( models included !!! )

I've had 400-500 m range before fail safe occurs ( PCM MC 18 Rx ) , Tx placed on my 3rd floor window, in a small houses and buidings ( 5 max floors) suburb of Versailles.

;) Now, it's difficult to talk of distance, as surroundings greatly modifies the signal transmission.

These days ... A friend of mine called me about a Fail-Safe triggering on its field at short distance : :blink: It was due to a giant water sprinkler for corn !!!

Model was just intended to fly at scale championships ... and receiver one of the lasts Multiplex " IPD" ones.

Thanks to God there was also my Glow Heather ( The Brain ) aboard wich entered into Fail-Safe idling the engine ...

He never had a glich in this place ... 'til this day - and the sprinkler.

Back to our subject, it's more a question of relative value than absolute value : it depends too much to environment.

But, same conditions give same mesurements ... It's valuable for verifying the radio once a year, or new component testing.

I'll make trails to get the "minimum usable signal value " as the signal disappears neatly instead of linearly decreases ( only at the limit !!! :huh: )

And also for Fail Safe triggering ( it corresponds to 5 wrong pulses in a row )

read you next time ... Duck liver and Sauternes are waiting for me !!! :D:D

Alain

Edited by Acetronics

Share this post


Link to post
Share on other sites

:D Hi, Mr Cam

I Think it's the simplest way :

1) To help for a rough tuning of the Tx head coils ... ( the more the light reddishes - the more HF power !!! )

2) to verify on the field the transmitter transmits something !!!

3) Not to burn the HF Transistor when no load applied to output stage.

Alain

Share this post


Link to post
Share on other sites

Hello everyone,

I want to give my 2cent of worth to the BAT-Channel of the receiver and the signal which we can see on a scope there...

I have a Graupner R700 RX and just done the test you suggestet. I also have the result that I either see a full signal or NO signal (only yerk) at all... so NO RSSI on that pin!!!

But what I have discovered is that the seen pulses are equal to the 7 or 8 channels of which the TX sends... pull a trigger or turn a pot and you will see that on scope.... a fast microcontroller could read in the duration of each of this pulses to get servo/channel-positions in digital without having to interface to each channel separately.... (think of the FMA copilot... LOL)

Greets,

Marcus

Share this post


Link to post
Share on other sites

How clever! a RX that gives you direct access to the demodulated PPM signal! That could be cool indeed for some projects :P

Now you can make a wireless trainer system in no time... and without paying for the expensive one that is sold ;)

Edited by Kilrah

Share this post


Link to post
Share on other sites
That could be cool indeed for some projects :P

Now you can make a wireless trainer system in no time... and without paying for the expensive one that is sold ;)

How clever! a RX that gives you direct access to the demodulated PPM signal!

Hi, Kilrah

Not clever ... just someting to permit an easy wiring for RX tuning and controlling at the end of the soldering process.

Just to save few cents ...

Alain

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×