Hitec Receivers

[kymbo]

I was transferring the receiver from my recently deceased ripmax evolution into a scratch built macchi on the weekend when I noticed it was only working intermitantly.

I checked the power supply,antennae and transmitter. All tested ok so it boils down to something in the receiver and micro electronics is not my game.

I checked for anything visually wrong on the receiver but no joy. The receiver is the one that came with a flash 5.

Anyone on here any good at fixing these things?

[thevon]

When you say it's only working intermittently, what's it doing? Firstly check that the radio's working fine on another plane. IF so, I'd be first doing a really thorough check of the connections. Be really careful to only wiggle one thing at a time. Pull some tension on each plug connection. Check that the crystal legs are pushed fully into the holes. Connnect the power lead up to a charge indicator/ voltmeter and twist the battery pack, wiggle and pull all the leads and plugs. I guess process of elimination first. Try a different crystal. If it still looks like the Rx, remove it from the case, connect it all up again and (gently) warp the board in different directions. If there's a fractured solder joint it will cut out when you bend it the right way. Probably no help but that's all I've got!

[kymbo]

By intermitantly I mean the model can be sitting on my work table working fine then it will suddenly twitch putting the control surfaces at a funny angle and there is no more power going to the servos(They have no resistance when you move them manually).

I checked the power supply by trying different points of input into the receiver and different types of power supply but the problem didn't change. I also tested the other plugs and made sure the crystal where properly in.

Surprisingly moving twisting the circuitboard as you suggest didn't seem to have any effect when I thought it would.

I bought a new receiver this morning $70 so I will check that out tonight but I would love to sort the old receiver out. I'm starting to remember what made me loose interest in this hobby last time

[thevon]

I wouldn't get too despondent Kymbo. You can get gear really cheap now and it's better stuff too. Have a look at the price of receivers from places like rchobbyboy etc.

[kymbo]

Thanks Thevon. That site looks good.

I was impressed by the rc warehouse site too so I went over there today. I ended up buying a new Hitec 6 chanel receiver and a micro 5 channel for my other transmitter. Hope to combine it with a small brushless and ecu I bought on a whim from ebay a while back.

They didn't have anything cheaper they would recommend so I coughed up the $110. They didn't have my crystal freq available.

Can someone explain in layman terms the difference between dual conversion and single conversion. The way it was explained to me today is it only has to do with the receiver and receiving crystal.

[thevon]

There are good explanations if you look online. All I know is it's supposed to reduce the possibility of interference. If the Rx is DC, then you have to use a DC crystal. But DC has nothing to do with the tx. There's no such thing as a dual conversion transmitter crystal.

I always used DC because the Hitec Rx's had it. But since using others which aren't DC, I don't think there's much benefit. I have some MZK receivers and they are better than my Hitec DC ones. But most of all, the Multiplex IPD Rx I got with my new Co-ckpit SX radio is the best ever and I have most faith in it for moldies. The Hitec super slim gets glitches but not the Multiplex (at Bald Knob).

This shop had the best range of crystals when I got mine www.hstore.com.au/

[skyboyken]

Hi Kymbo,

I'll try for a short and (hopefully) useful explanation of single/dual conversion.

The receivers receives a signal comprised of a carrier of around 36MHz which has superimposed on it a data signal of up to around 2KHz. The receiver 'sees' this as one frequency which varies by approx +- 2KHz around the central freq of say 36.010 MHz (for channel 601). So the first thing the receiver has to do is 'strip' the data signal from the carrier. It does this by mixing the received signal with a signal that it generates which is slightly different. That's called heterodyning. After the heterodyning step the signal is put through a bandpass filter to strip out noise, and then it is amplified and processed.

If there is 1 stage of heterodyning to reduce the received signal to data, that is called single conversion. If it is done in 2 steps rather than 1 that is called double conversion. In theory double conversion can better help reject interference because there are 2 sets of bandpass filtering to reduce noise. In practice though there are a bunch of other factors in receiver design which have at least as much effect. Some of the best performing receivers around are single conversion. Schulze receivers for example.

My suggestion is not to concern yourself about single/dual conversion beyond making sure you put a single conversion crystal in a single conversion receiver, and so on. You are right Kymbo when you say that none of this has any impact at all on the transmitter.

Kymbo, you sound like you've had equipment trouble in the past. I'm sorry to hear it. I've had my share of problems too. FWIW I find that buying quality receivers and servos works for me. The equipment is reliable and I can just enjoy my flying. Whenever I try to save money I get problems and I end up spending more because I have to buy twice to get a good result. My experience is that every single cheap servo and receiver I have bought has ended up in the bin, and every single quality servo and receiver is still in use and performing well.

I hope this is of some use to you.

Ken.

[kymbo]

Thanks Ken, I did understand that. I spent a couple hours searching around the web including Hitec's site and didn't find any explanations as clear as that.

Its funny that you mention the slimline Thevon that is the receiver I am having problems with.

On the same subject but a bit different, I notice that most the yanks operate in a 72Mhz band width. Are their transmitters and receivers physically different or is it just the crystals. The reason I ask is that I'm going over to Hawaii in a couple weeks and I was thinking about checking their prices if they are compatable. I'm always hearing how we pay unrealistic prices compared and there is bound to be some hobby shops in Honolulu ;D

[Pij]

Some slopes too, unless I'm mistaken! Try Diamond Head at the end of Waikiki. Or go for a drive up the mountains. There must be a powerline clearing there or something, so if you can see through the almost permanent cloud...

[skyboyken]

It's been quite a few years since I went hobby shopping in Hawaii but there used to be really big and cheap hobby shops. Ala Moana mall IIRC had one.

Be careful buying 72MHz transmitters and don't buy 72MHz receivers. Any transmitter that uses an RF module is fine to buy, but you'll have to throw away the module it comes with and buy a 36MHz one when you get back to Oz. Receivers don't use a module and cannot be physically changed (economically) from 72 MHz to 36MHz.

FWIW your best option may be to buy 2.4GHz. That way both the Tx and Rx (es) can be used in Oz without change.

You can buy as cheaply on the Net as you can from shops and postage on radio gear isn't too bad. If you want to save money buy planes and bring them back! The postage costs are about $300 for a 3m mouldie for example.

Go Great!

Ken.

[thevon]

I'm not sure of this but I've heard people saying that some Rx's work really well with 72mhz, but they're not so good on 36mhz. The Hitec SuperSlim is considered very good in the USA, but perhaps it's not so good on 36. That's anecdotal of course.

I took my Superslim out of the Wizard and put in a big Supreme (the big Hitec Rx which should be really full range). Flew it for the first time today and it's still getting some glitching. No dropouts, but jiggling ailerons/ flaps in particular spots of the sky. Whereas I know that the Fazer with the Multiplex Rx has absolutely no glitching in the same place.