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Hi everybody,

Recently i was drawn to these cheap and cheerful 1.2ghz cams that are being sold on ebay. Paying just 20 uk pounds and delivered to my door in 5 working days it seemed a bargain. Rated a 200ma as per Mr rc cams test model,range seemed good with 400ft ground level. Once in a model aeroplane things were not as good with just 200ft and broken images. I suspected low TX output and poor RX aerial to be the problem. The fact is that the equipment is very good value for money but you do get what you pay for.

My first test will be building the GP Patch and I will report back soon on my findings.

Question : Is there a way of tweaking the TX power on these units? I known Mr RC Cam found his 200ma Model was only transmitting 40-50ma of rf.

As a keen electronics and rc hobbiest I will of coarse be having a play and looking for improvements. Will keep you all posted!!!

post-5-1094492943_thumb.jpg

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Increasing RF power would probably require adding a typical MMIC RF amp chip. They are low parts count sort of solutions. A Google seach will cough up some good info on MMIC's.

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Thanks for reply will look in increasing RF power slightly.

Under normal conditions you have to double the RF power to see any noticeable changes in a TX's range so I'll be looking for at least a 100mw of radiated power.

Noticed also my TX monopole was 4.25" -very strange length at this frequency.

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Hi, If I were you I would look at getting a 2.4ghz system. It will be cheaper in the long run, plus it is legal ( up to 10mw anyway ). 10mW may not sound to good but some of us have done better than 1/4 mile with it which is better than you are doing now. Also there is more stuff and info for this frequency so you will have more options :o)

Good Luck, Terry

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Thanks for the info Terry,

I must admit I never intended to use this equipment as my main system. It was more of a experimental project and at £20 it doesn't matter if I damage it through modding.

I have currently only seen one uk company selling a complete setup at about £165. I would be grateful of any info or prices of other current 2.4ghz equipement available. If company names and price's cannot be displayed here please mail to :-clubmail-AT-tiscali.co.uk which is our club address.(west Essex Aeromodellers)

Myself and others would be interested to know which 2.4ghz equipment and aerial combinations you and your colleagues have had best results with at 10mw. (yagi / patch )

Kind regards, Mark.

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Yep, I use Maplin,also www.bitztechnology.com and www.lprs.co.uk for modules if you can handle a bit of basic electronics. I use my own design patch on the rx and basic dipole on the tx.

Terry

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Thanks everyone for your comments and info.

Has anyone tried using the below setup from this company?

http://www.rc-cam.co.uk/Products.htm

Anyway about to construct a re-scaled patch antenna for my 1.106ghz Hong Kong Phoey setup. Will publish my results here in the near future. The weather in the UK is not looking too good for the next 4 days so in flight testing might be put on hold for a while. :(

Regards...Mark

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Kit looks ok, but the price is high. You can do the same thing for much less if you mix and match from the links we gave you.

Terry

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Although the website says so, I can identify no part of this that is made in the UK. That should be your first (and last) indication of what type of seller you are dealing with. Anyway, I wonder where they got the clever trade name "RC-Cam?"

T.I.

Edited by Temporary Insanity

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I think you will find they only mix and match the parts then sell it to you as a ready to go set. Like I said it cheaper if you do it yourself !

Terry

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The only thing that they seem to do themselves is the dual camera switch and PCB on the TX.

The RX is the one that comes with a 100mW HK system, and the CMOS camera comes from an European electronic components dealer (we've used the same). I believe they throw away the 100mW TX (much too big) and keep the cheap RX.

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Hi everyone, some interesting comments on the so called all British made cam.

I have now constructed a Patch antenna for my Hong Kong Cam setup.

First a point for people intending to purchase one of these setups.

The seller assured me 100% the cam was 1.2 GHz but that was rubbish. A freq counter proved that 1.106 was the exact frequency. So most of these cams on EBay should be sold as 1.1 GHz models.

For those of you that have a 1.1 GHz setup here's the re-scaled patch dimensions.

LARGE PLATE = 232mm

SMALL PLATE = 123mm

SPACERS = 10.85mm 11mm should be ok

Try to keep the material as thin as possible as this is a fairly large antenna to support on a single connector (over 2 xs larger than 2.4 GHz ver)

Everything else is as per the design on this web site. I used a redundant fishing tripod stand to fit the receiver on.

TESTING

Although in flight testing has not been possible yet I have conducted a number of ground tests. Initial line of sight tests showed an increase in range of about 3x (1000-1200ft) over the standard supplied wip. Picture quality was also improved with far less broken images on a moving target.

Even built up area testing was greatly improved. This aerial would probably work well in a large warehouse environment were the standard wip would not have enough gain.

Conclusion - Very pleasing results and well worth constructing.

My Sardine Can has been promoted to Tuna Can.

Next time I'll go to work on the TX and see what can be done to improve 1.1 GHz transmissions.

From Tuna Can to Salmon Can -we will have to wait and see!!!

Any questions fill free.

Regards...Mark

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Thats great ! sounds like you have a winner there. 1.1ghz output is another reason to steer clear of things I think though.

Just out of interest I wonder if you can do a simple test for me ? Can you refit the dipole/whip aerial on the rx and hold a metal sheet reflector 1/4 wave behind it and tell me the difference ? Its a little test I do myself to proove the effectivness of my aerial designs, a sort of benchmark.

Thanks, Terry

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Hi everyone,

In answer to your question Terry I conducted some tests today.

By adding a ¼ wave reflector to the original whip I found a medium increase in performance. The results were about ½ the range of the patch design.

Using the half wave dipole as ref to 0db I would expect a 3db increase in signal strength using a rear reflector. This should equate to around 1 ½ to 2x range which is roughly what I found during testing. I don’t know if this matches your results but I consider my findings to be only approximate.

This brings me on to my question of how does a patch antenna receive up to 8db’s of gain?

The rear reflector should give us an instant 3db increase, however how is the remaining 5db achieved without use of directors?

Any comments from patch experts appreciated.

Regards…Mark

Edited by modelman

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Using the half wave dipole as ref to 0db I would expect a 3db increase in signal strength using a rear reflector. This should equate to around 1 ½ to 2x range which is roughly what I found during testing.

The +3dB gain would translate to about 1.5X range. If you see 2X range, then the gain increase is +6dB.

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Thats a great site you found mark ! I designed my patch based on all the patches I had made from web sites as when I got a reflectometer I tested them all and found they were not as good as I thought. That site you found says that the band width is only 3% so that may well be the main reason. I use a round element on my patch which was not covered but it seems to work just the same.

Yes I do seem to see 2x range increase but I dont know why it should be that high. I use a reflector when doing testing as it reduces the effects of objects near by and also gives a closer signal strength to my aerial under test.

If you like playing then try making a 60 degree feed horn out of cardboard covered in tin foil, you may be surprised, I was !

Terry

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I'm glad our test results matched. We must be doing something right!!

I will have to get round to trying the cone and see what extra gain can be grabbed.

Some other sites suggested that a correctly assembled patch had a 65 degree horizontal and 75 degree virtical angle, forming in fact an oval shaped radiation pattern. I'm not quite sure why this is but maybe something like ground effect makes the angles different. I'm no patch expert yet but I'm learning.

Regards...Mark

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Ive not seen those figures quoted but I find a plain patch (no horn) works to almost 180deg but it still has a noticable drop in gain only 15 to 20deg off centre.

Terry

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UPDATE TO MY 1.2ghz PATCH ANTENNA TEST

Myself and 10 other modelers finally got round to doing some detailed in air testing with my rescaled 1.2ghz patch. The results were almost unbelievable compared to the original supplied whip antenna.

1) Range was increased from 200ft to as far up as we could see the 60" model to control it. (800/1000ft)

2) Coverage was around 180 degrees arc with 90% unbroken images throughout.

3) Antenna even worked when flying behind it. Very strange but not such strong signals.

4) With 45 degree elevation and flying in front of antenna no repositioning was needed at any time.

CONCLUSION

This antenna exceeded all our expectations. We hoped for a small increase in performance but not to this degree.

If constructed correctly this design will improve any systems receiver and in our case by around 500%.

Simple to make with very good results why not give it a try!

A note on construction.

Pay particular attention to accuracy when building a patch and try to obtain your TX's exact frequency. All my element dimensions were within 0.5mm and spacers 0.2mm

A patch only has around 3% bandwidth so to achieve the 8 or 9db's of gain matching and size is critical. Spend a bit of time on your dimensions and you will be well rewarded.

Regards...Mark

Edited by modelman

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Hi Modelman.

I am new to this equipment, but have just obtained the same Hong Kong bits plus a USB converter so that I can see the pictures on my laptop. Working quite well, not flown yet, but being built in to a housing to go on my 73 inch Laser 150 powered Mystic. What I am not yet able to do is record on the laptop. Does anyone know what software I need to do this with XP. Clicking a button on the USB converter does record still's.

First trials were not brilliant. The 9 volt power soon failed (PP9) and the receiver had to be re-tuned quite often. I have now connected the receiver to my flight box 12 volts and it is much more stable and gives a better range. Your talk about airials has me confused, I have not had time to study this, but are we talking about the camera airial or the transmitter? I see from somewhere that the plug supplied for power has a voltage regulator built in. By removing this and hard wiring would the camera run on a standard 4.8 volt NiCad?

I am Hemel Hempstead, Uk and a regular visitor to Maplin. I now need a suitable 12 volt TV which I can take to the field, any idea's?

One gets what one pays for, but for about £50 the Hong Kong bits are good value and came within 7 days. :)

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Hi Mark, I agree with you that you need to get the sizes as close as you can, I found that even 0.1mm makes a fair difference when tested on a reflectometer.

Hi Engineman, I use a Pinnacle video capture unit that works well with the software supplied but I have also use Pinnacle Studio 8 software with it so I can edit it. The camera aerial is the transmitter aerial but we are talking about the receiver aerial on the ground. There are lots of monitors you can use, you just need one that suits you and your pocket !

I use an LCD unit made for in car use as it views well in sunlight (plus it was cheap in a sale)

Terry

UK

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Hi Engineman,

Try to run the RX from your model boxes 12 volt supply.

Use a good quality 8.4 volt rechargeable battery on the TX. This should give you around 2 hour’s continuous running on a Hong Kong 200mw cam setup.

You may still not get the desired results in terms of range so I strongly recommend constructing a patch antenna.

As Terry rightly confirmed try to keep all dimensions as accurate as possible and you should obtain a 3 to 5x increase in range.

A quick question were did you get your Laptop VIDEO to USB converter from and roughly how much did it cost?

Ragards...Mark

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Hi everybody ! Congrats for this forum creators and to all users that help improving our wireless cams.

I would just ask some help on these HK 1.2Ghz sitems.

I bought some of these Hk cams, they were cheap, and looked nice. I was trying to put them on some RC models but as i'm never satisfyed with things the way they come from factory, i decided to disassemble one to see if i could extend the TX away from the cam. Well, i did that but on the way i've ruined two of them by doing some changes and forgetting to check polarity. The stupid part is that i did that twice ! On different ocasions! That small PCB or SMT , can't remember, with the LM 7805 5V reg and the other parts, wich i don't know the name, the tiny brown ones, whent down.Trash!

Well , the question is , is there a way to replace that stuff with a simple and bigger part or device to do the same job like the Vreg ?

I would apreciate some help from you guys because i'm just a curious guy who like to mess with things just to better know them.

Keep the good work , cheers Joao Catarino, Portugal

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