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ahab

how long can the coax be on TX

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Hi there

can anyone shed any light on how long i can make the coax(RG174A/U) between my 2.4GHz Tx and The YB2normal ground plane ant?

I realise the answer is probably going to be "short as Poss" but as I plan to fit the Tx in a scale model I need to know just how short it needs to be

Edited by ahab

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As you say 'short as poss'. There is no correct answer to this as it depends on what power you need to radiate ? Is it not possable to mount the tx module close to the aerial ? If there is no other way then I would use a more powerfull tx to compensate for the co-ax and use a better co-ax than RG174 if you can handel the thicker stuff ?

I have used up to a foot of RG174 for a dipole that was fitted to a drop down arm on the bottom of my plane which worked ok, the dropouts were less but the overall range was also less. I changed it later and hung the tx module on the arm which was better still as the range almost doubled. I dont bother now as I have a more powerfull tx but this was when I could only get my hands on a 10mW module. Can you tell us your proposed setup ?

Terry

UK

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Thanks for the reply Terry

I plan on using the TX on a scale bipe and rather than chop holes in the bottom of the fuz I wanted to put the tx module and Nicad in the cockpit and perhaps trail the ground plane ant out of the cockpit. with the YB2normal ground plane ant does the element point up or down?

Until I get the range I want and the stability (no dropouts) I am using one of the Cheapo cmos cameras that came with a Hong Kong 1.2 GHz setup. I am planning on having the camera mounted on the fin facing forward . The Tx and camera are both 5v so I will run them from a 4.8V nicad. When I get the setup working well I will invest in a 12v ccd camera for the quality.

I picked up a pair of Olympus eye treks for £77 ($146) on ebay and these will give me a stunning view. I Hope

Thanks again

Ahab

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The element points down but Im not sure trailing it will be good, maybe use some servo tape and fix it ? 'No dropouts' will be hard to do unless you use a fair bit of power, fly close or very level. Have you seen the diversity systems talked about on this forum ? I hope you dont want to do aerobatics ?

Terry

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Ok Teery I'll try the servo tape as you suggest.

By The By Maplins are doing a frequency counter ans signal strength meter fo fifty quid will that be usefull for tweaking ants etc

How would you suggest adding more power to the TX

I'm not an aerobatic freak so Ill try and keep close and level

where would I find this DIVERSITY thing?

Ahab

Edited by ahab

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DIVERSITY thing here http://www.rc-cam.com/forum/index.php?showtopic=653

I have a meter like the one at Maplins which is ok for some side by side testing but its not very sensitive so needs a pre-amp to be of much use.

I dont know what TX you have but Im guessing it would be hard to get more power from it, you realy need to upgrade to a more powerfull module / TX to go this route.

If your going to fly close and level your in with a fighting chance ;)

Terry

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Terry

If I dumped my present Tx where would you suggest I get a more powerful module

all my searches come up with 10Mw stuff while I'm guessing i'd need about 1watt?

Ahab

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Ahab, try tinywireless.com he has transmitters up to 2W!! Its where I got my 400mw system, and my awesome CCD camera. Really good prices, too.

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Yup Thanks for that I was really looking at 2.4Ghz to be legal in UK and also its gotta be a PAL camera

Edited by ahab

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If you want to be legal in the UK you can only use 10mw.

I dont use over 250mW and have never found the need for any more as it exceeds the rang of my R/C. I surgest you start with a good 10mW setup and see how it goes for you, I use 10mw most of the time and fly up to half a mile away ( with dropouts ), 1/4 mile is almost dropout free.

Terry

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Thanks terry I'll bear that in mind

on your system what ants are you using

Edited by ahab

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I use a dipole on the tx and a home design patch on the rx normally, quad patch or helical and preamp when I want max range.

Terry

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Jeez I think I am fast getting out of my depth here

I think I will have to save the pennies and go with a diversity RX and whatever TX, camera etc that Black widow can supply

Thanks for you input Terry

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I was just thinking, if you need a dropout free picture can you use a palmcorder in the aircraft ? I asume you want to record it as you want a dropout free picture.

Terry

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I thought of that but I want to equip existing models and there a'int enough room

http://www.spystoreuk.com/videotx.html#2-4TX

are doing a pocket sized recoder (memory card) for around £200

what do you think

I dont think I mentioned it but I picked up a pair of Olympus eyetrek gasses on Ebay for £77 absolutely brilliant. Have just got back from flying and tried out my Hong Kong 1.2Ghz gear. I built a scaled up Goof Proof Patch and mounted it on to the RX with an F connector ( from what I have read I guessed that my 1.2 set was probably 1.1 so I scaled the patch to that size)

The tx ant was 110mm long so I lopped it to 65mm The results were astounding !!! Flying a 1/5 scale stearman a long way off (400m?) I had some dropouts and the cmos camera quality was crud but heck it worked

I had the camera facing forwards attached to a cabane strut with the pp3 taped to the strut and I viewed through the eye treks while my mate flew then we swapped over.

The eye treks do need 240V but I have an inverter so it was portable

We are having a bit of a vibration problem as the camera was hastily fitted and may not have been shock proofed enough , any ideas on camera mounting.

The next trial will be with my 5m scale slope soarer ASW17 . I will attempt to fly the beast through the eye treks with my mate on a buddy lead for safety.

Ithink I wil still go with black widow and diversity though. I am just waiting for them to get back to me with a price

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I've used both of these recorders. The "memory card" one is a Mustek PVR-A1. Records in 320x240, "HQ" mode fills a 256Mb SD card in 15-30min. Handles a 1Gb card perfectly. 110gr only.

The other one shown is Mustek's last one, the PVR-H140. Records in 640x480 to a 40Gb HD. Quite better quality, but it's also quite heavier (290gr)and bigger. Maybe that's a bit too much for a standard-sized plane.

Both record in MS MPEG-4 format, in ASF files (like WMV) like all these pocket recorders. Can be very easily used in Windows movie maker, but unfortunately very few other programs can open it. As I do all my video editing with Adobe Premiere I used to convert the files to DV before importing them in Premiere.

The PC video conversion software is awfully slow and crappy, so if you want to be able to watch movies on it during trips it's not the best choice. Only used it to record video at the field. I'm now using either a DV camcorder or a RCA Lyra RD2780 (like the H140 but in 320*240 and 20Gb only, but handles more video formats).

If you want I can try to find sample videos of both Musteks in my archives.

For the eyetreks, if you want to get rid of the AC adapter just get a 2-cell Li battery or 6-cell Ni.. one and connect it to the DC in plug. Used a 7.2V/1500mAh Li-ion, it worked perfectly with around 4 hours battery life :)

(also valid for Sony's PLM-A35 :P )

Kilrah

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Wow you are a MINE of information

My plan was to have a camera in the plane with a 2.4GhZ TX and an RX and recorder on the ground do you think the Mustek is the way to go for good qiality or not

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Kilrah

I would love to see sample videos from your musteks if possible

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If you want to record on the ground then the best quality you can have is with a DV camcorder. But it's also the most expensive one like always.

Got a few samples, judge for yourself :D

On the ground with PVR-A1

From a R/C airship, PVR-A1

These 2 are raw output.

And for comparison:

From a plane (A1 again)

This one has been taken into windows movie maker to be cut, the whole file was 120Mb. No noticeable quality loss (2Mbps WMV)

A few minutes later, but recorded in DV and compressed to 2Mbps DivX

Don't have a H140 video at hand now, maybe tomorrow ;)

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Thanks for that Kilrah I will look at the comparisons when I have finished this

Let me explain my dream

I would like to be able to get dropout free good quality video from my plane, record it, save it to PC, Burn to DVD the watch good quality stuff on the TV via DVD player.

To date I think the way to achieve my dream is to aquire

Black widow diversity RX

BW 200mw TX

BW ccd camera

Mustek pvr-A1

DVD writer

How does that sound for a viable proposition

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If you want to watch on a TV it should be OK with the PVR-A1. As the quality of a TV screen is much lower than a PC monitor's, most of the time you don't see the details that seem obvious on a PC. If your computer has a TV-out plug, you can try playing my samples and watch them on the TV.

The PVR is also cool as it's really small and handy on the field, compared to a PC or a DV camcorder.

I think then the dropout free RF link will be more of the issue, not the recording. It depends of how far you want to fly.

The last 2 samples were made using a 500mW TX. You can see there are some short dropouts sometimes, even if we are flying close. But these should be eliminated by the diversity receiver.

Otherwise that sounds like a good choice.

BTW, I have a PVR-A1 that I could leave for £100+shipping if you're interested :rolleyes::P

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Thanks for tha adivece Kilrah

I dont have a tv out on my pc but I do take your pint aboutb the Tv quality I have a 32" plasma and you need to sit 5m away to get the full effect.

I dont plan on doing any "cross country" flying so a TX that will give normal flying range should do especially with the Diversity RX

Thing is I fly power and slope and I really need a complete setup that I dont mind hauling up a hill ( just order a 7.2v 1300MaH Nicad for the eye treks Thanks for the advice)

Thanks for the offer on the A1 but I can get one here for £115 with a 512 sd card ( unless I'm looking at the wrong thing :D )

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That's a good price for the A1, if it's correct then go with it ;)

Here is a video that that was recorded with a PVR-H140. It has then been edited in windows movie maker, but the video is still good. Haven't found a piece of raw video :unsure:

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