I wrote to Thomas on Sept 23:
Hi Thomas, the mailman brought a toy today. It's your system. So far I'm
impressed with it. It works right out of the box with my 9ZAP, round din
plug and all. And I can't tell a difference in the servo movement in it
versus the FASST system I was using. And I don't need a module in the 9Z for
it to work, so I'm using about the same power from the batteries with your
system. All my previous trim positions appear to be unchanged as well. The
failsafe positions were fairly easy to set also. And yes it was fun touching
the antennas and watching the leds switch back and forth. So what you've
been wanting know comes next, the range tests on ground.
I started without camera system to get a baseline. One RX antenna mounted
horizontal, and the other mounted vertical. Thomas, I'm guessing the wire
you soldered on is the part which does the receiving? I made sure these were
straight one horizontal the other vertical and away from each other. The
receiver is two feet away from the motor controller and more than a foot
away from the ATV transmitter.
I shortened range by removing rubber duck from your rc transmitter. And went
about 85 feet away before control was lost. I turned the plane around and
did it again and control was lost in exact same distance.
Now for the camera. I use a 910mhz 500mw transmitter. So I setup my ground
station at the point where range was lost without rubber duck. Goggles,
receiver, dvr, everything I've been using for fpv turned on. And I got the
SAME range check with all this turned on at the same distance and with
different plane orientations so this means the rc RX is unaffected by the
910mhz video. And so far I can't tell if the 437mhz frequency is
interfering with the video in any way, even when I wave the rubber duck in
front of the patch. I have yet to try the 7W booster though.
So it has passed the ground checks and later this evening if the wind calms
down I'll try it in the air by direct visual first. Then by fpv as I've been
I have a 30 foot RG58 cable now with bnc connectors on each end to connect
the transmitter to the booster.
Possible ham inteference
I wrote to Thomas again later on Sept 23:
Hi Thomas, you once said your system could not be detectable. See post #22
in your thread on rcgroups. However, I did a test sitting right next to my
ham radio, (Kenwood D710A). I set the frequency to 437mhz which was silent but as soon as I plugged in the rc transmitter it not only broke the squelch but gave a S9 on the meter and sounded like white noise. Granted I couldn't tell what the noise was from, but the noise was there. So I tuned the radio past 437mhz and still got the noise on up to 440mhz with a decreasing S meter reading, same thing below down to 434mhz.
After he responded to say I was overdriving my ham radio I did some more testing:
My antenna was probably about 20 feet (my ham antenna) from me. But I did as you said and removed
the rubber duck and tried it again. This time I only got the interference
like you mentioned. This makes me feel better about using the system. But
it's not right on 437mhz, the center seems to be 437.250mhz and is
detectable a couple of channels above and below that just like you said.. It
sounds like a really bad phone connection with sort of a hum to it. I
tried this again with the rubber duck and set the transmitter on the other
side of the yard and got the same thing. Center on 437.250mhz with a couple
of channels above and below too but not the terrible noise I got before. Did
you set it for 437.250mhz? That was probably a good choice as the lower
limit I found for video interference was 437mhz.
So, I tried it for real yesterday. I flew my telemaster out to about 1.5
miles and came back. The wind was blowing 10-15 mph up there in the wrong
direction so it wasn't a good day to go any further. But the system was rock
solid all the way. I even tried to get it to fail by pointing the rubber
duck straight at the plane but it wouldn't.
Some more on the video interference at 910mhz. I noticed the goggles
(rvision) seemed to be affected by the strong rf but only when the rubber
duck is 2-3 inches or closer. While in flight and 1.5 miles away I waved the
rubber duck in front of the patch several times and got some wavy lines of
interference. When I got home and reviewed the video I could hear the pulses in the sound. Not all the time but at different points in flight both near
Today I'm going to try the 7W PA (with antenna), and maybe the evening when the wind calms down I can fly again.
Last edited by Carlyle Harper; Sep 24, 2008 at 07:06 PM. Reason: added title
So this evening I tried the 7W PA. My antenna was this, thinking it had to be better than the rubber duck:
Using the 7W PA and this antenna, at 1.5 miles out I started getting severe glitches. I was flying fairly high, don't know exactly how high though.
I was able to turn the plane around back home. When it came back in sight I quickly turned off the PA and put the rubber duck on the transmitter, then flew back out again to the same spot with no glitches, in fact I tried to get it to fail again by pointing the antenna at the plane or at the ground.
I was powering the PA with a 2s A123 pack, 6.6v. The PA draws 1.5 amps with this being fed via 30 feet of RG58 from the transmitter.
Another note about video:
The antenna with the 7W PA was about 30 feet away from the patch. During this flight I tried turning off the transmitter to notice video quality. I didn't see any noticeable difference. And as stated in a previous post I didn't appreciate any change in range during the range check with AVS transmitter on or off.
Now why did it have glitches with that much power and an antenna larger than the rubber duck? Do you think I was flying so high that I was actually out of the gain area from the antenna?
Thomas didn't you say the same rubber duck could be used on the 7W PA?
It will be next week before I can fly anymore for sure and try the rubber duck on the PA if that can be used.
Last edited by Carlyle Harper; Sep 24, 2008 at 07:27 PM.
Another note on video quality:
During this flight the 7W PA and antenna was about 30 feet away from the patch. I tried turning off the rc transmitter but didn't notice any change in video quality. I'm using 910mhz 500mw video. And as stated before, during the initial range check I did not appreciate any difference in range with the avs transmitter on or off.
Good news with the 900MHz video TX dont jam the UHF RC system !
>at 1.5 miles out I started getting severe glitches.
I think you talk about RC link glitches with the booster and the new long antenna, that sux, now we need to know why:
the antenna you got how is that mounted, and where ?
the radation patern how is that ?
your plane position in that radiation patern ?
check RF power from booster using UHF wattmeter if possible,
the cable from booster to antenna is that good ? (I have seen standard RG58 cable on antenna feets have 3dB loss for only 3m !!)
the antenna have good swr at your frequency ? if hight cable loss you will be cheated to measure better swr !
measure swr and change frequency and see if this helps !
and yes the little antenna can handle the boosters power :-)
ok so we can agree your video range is NOT limited due to RC system !
and not due to 7W booster ! that is good news for me at least :-)
1.5 mile = 2.414016 kilometers should be easy to handle with 500mW and little antenna !
with more power from the booster you should get MUCH longer range,
we need to isolate the booster or new antenna to find out what is ok and not
please try to combine new antenna with 500mW directly,
and booster with rubber antenna and then see your range.
Last edited by thomasscherrer; Sep 25, 2008 at 02:51 AM.
you guys incorporating OSD with this system?
is there not a sensor that can messure the rx (plane) reception?
and the rx video reception?
"Kapton tape" could be also usefull in FPV set ups.
really cool vid
I might just have to do what you said Thomass and buy one of yours and sell mine brand new used.
Last edited by David22; Sep 25, 2008 at 03:34 AM.
this UHF RC system is "just" a long range RC solution
it is specially uptimized for the range thing :-)
you can modify the receiver: to output RSSI signal in CH8 connector:
this voltage can be read out on OSD's that can accept external signals,
one to mention is IFOSD that will let you calibrate any voltage to be read out as anything you can imagine, you can also make a bargraph show the rssi
look near connector ch 8
Normal default, CH8 servo in the signal pin, +5V in the supply pin.
R19 = 0R
R20 = Not Mounted
RSSI Out on power pin, still ch8 pulse out on signal pin:
R19 = Not mounted
R20 = 0R
be sure your mesurement on the rssi signal have hi impedance !
resistive load over 100k
and capacitive load under 100pF
this system measure FAST changes on the RSSI signal from antenna switching,
so in case one antenna is bad you will see a short low peak,
if you sample the rssi analog signal in phase with the antenna switch
(LED signals) you can read out both antennas rssi
>I might just have to do what you said Thomass
>and buy one of yours and sell mine brand new used.
you are welcome, I am ready to take your order,
simply read post #1 and email me, then I send you my paypal adr.
Thomas, since the system is glitching and your system is CRC checked anyway, isn't it possible that the glitches is the result of the high RF getting back into the PPM stream feed. While testing my own system, I found that with a proper CRC corrected system, it is impossible to get glitches (kinda like PCM systems) except for switching into failsafe. If the behaviour is really glitching, then I would guess that you need to do something about the connection between the 9ZAP and the transmit module. I would use shielded cabling, and maybe even some RF chokes on the line. This could resolve problems arising from RF getting into your PPM stream and corrupting it.
good point Daniel, I do use shilded cables for power and PPM input
and the PPM and supply input is also carefully filtered inside the box,
I have used this system for many years with 7W, 25W and now also 240W
I have newer seen a thing like PPM input jam,
but ok other tx systems could be sensitive if they are located too near the booster antenna, then his problem will be the same no matter what distance his plane is,
it is known to cause problems with some RC TX systems if you talk in cell phone while flying ! the GSM/CDMA pulses create jam inside the analog signals in the TX
and that gets out on the PPM stream, so leave your cell phone in the car :-)
we have a rule against cell phones in my club, they are not alowed near pilots that fly.
I think his antenna have too bad swr and maybe his rg58 is of the bad type with tons of loss and badly shilded, or maybe his antenna is a magnetic grounded type that
MUST be placed on a car roof to work, maybe he forgot that, so plenty of things we need to know to find the issue, I am sure it can be explained.
>at 1.5 miles out I started getting severe glitches.
>I think you talk about RC link glitches with the booster and the new long >antenna, that sux, now we need to know why:
>the antenna you got how is that mounted, and where ?
- Yes with booster and new antenna. It's magnet mount and on the roof of my truck which is metal. I have used it with ham radio to contact AO-51 satellite.
>the radation patern how is that ?
- Can't find a radiation pattern but the specs say it has 4.1dbi gain in a 1/2 + 5/8 wave configuration. I can imagine if an elevation pattern existed it would look kind of flat.
>your plane position in that radiation patern ?
This could be the problem now that I think about it. Maybe this antenna was intended for ground communication. I was pretty high up at 1.5 miles out and could have been out of the gain area of the antenna.
>check RF power from booster using UHF wattmeter if possible,
Don't have a UHF wattmeter.
>the cable from booster to antenna is that good ? (I have seen standard >RG58 cable on antenna feets have 3dB loss for only 3m !!)
I have no idea of the loss. There is 12 feet of RG58 that came attached with the antenna, and this went to the booster.
>the antenna have good swr at your frequency ? if hight cable loss you will >be cheated to measure better swr !
>measure swr and change frequency and see if this helps !
I do have a UHF SWR meter, and it measured 1.3 swr at 437mhz.
>and yes the little antenna can handle the boosters power :-)
Ok, it will be next week before I can try again and I will try the rubber duck on the booster then.
>ok so we can agree your video range is NOT limited due to RC system !
>and not due to 7W booster ! that is good news for me at least :-)
>1.5 mile = 2.414016 kilometers should be easy to handle with 500mW and >little antenna !
Yes, it is, in the same flight I switched back to rubber duck on transmitter for 500mw and went back out to 1.5 miles with no problems, even tried to get it to fail again but couldn't, it's just got to be that mobile antenna.
>with more power from the booster you should get MUCH longer range,
It was true glitching, I had camera tilt set to a default position in case of failsafe and I could defintely tell it was going there. Receiver went into failsafe about three times at 1.5 miles out.
>we need to isolate the booster or new antenna to find out what is ok and >not
>please try to combine new antenna with 500mW directly,
>and booster with rubber antenna and then see your range.
Ok next time I will try this, but it will be next week. On vacation this week and going to a meeting this afternoon so have to get ready for that.
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