Im thinking of getting a new RX for my Alfa MiG, and was considering this...
Do you think this is suitable for anything other than a park flyer?
Can anyone recommend a cheapish PCM RX? Thanks
David Bevan
6000+ feet (over 1800 meters). I do not know if units for other markets are different.
In the US market, PCM receivers are proprietary; meaning if your receiver is Futaba, it can only understand the signal from a Futaba transmitter. Again, that may or may not be a marketing scheme unique to our market.
| Im thinking of getting a new RX for my Alfa MiG, and was considering | this... | |
Most RXs have ranges around 1.5 miles -- 2400 meters.
At 300 meters your plane will be pretty high up, but not so high that you can't fly it anymore. Glider pilots routinely fly two or three times that height ...
| Do you think this is suitable for anything other than a park flyer?
Probably not. A slope flyer would be fine -- anything you keep close in -- but I wouldn't use it in anything I want to fly very far out. It seems wierd to make a PCM receiver with such limited range ... | Can anyone recommend a cheapish PCM RX?
Cheap and PCM don't usually go together.
You'll probably need to stick with Futaba -- PCM equipment is not usually compatible between vendors -- so your cheapest good option is the R138DP at $100 in the US.
If you need something small, I'd suggest just going with a good PPM receiver. Some of the new ones, like the FMA M5 and Quantum receivers, and the Berg receivers reject interference much like the PCM receivers, and they give you full range, are smaller and cost less.
NO!
Cheers -- \_________Lyman Slack________/ \_______Flying Gators R/C___/ \_____AMA 6430 LM____ / \___Gainesville FL_____/ Visit my Web Site at
"Cheapish PCM"? Good luck!
A word of advice: in electronics, you usually get what you pay for.
I find the assumptions being made here rather amusing. What's the range of a given receiver? Depends on a lot of variables not the least of which is the power out of the Transmitter. Why I've seen a miniscule three watts go
23,000 miles without a hitch.Our radios are all generally under one watt in power but, they seem to pretty well cover the full spectrum between .1W and a full Watt (from the factory). So 300m may be quite good if the Tx is only pushing 100mw.
On the other hand, considering the make of the Rx, I suspect 300m is a conservative figure. Especially since they're using it in their adds. This is based on the fact that they center tune their Rx to the band. This will cut down on the Rx sensitivity the further from center you get in your channel selection. Reduced Rx sensitivity will reduce your range also.
If you know someone who can tune it, you can have the new Rx matched to the Tx you're using and I'll bet the range will almost double or more. But this would make the Rx less agreeable to random channel swapping without retuning it again.
On the flip side, I've flown .40 size trainer models out to 1/4 mile away (measured). Most people (in spite of claims that will pop up) can't match that. They lose the visual acuity to maintain control of the model at that range. A quarter mile is 400m more or less.
Best bet? If this is the Rx you want, then get it. And before flying it, set up two test flight packs. Same size freshly charged batteries, same servos, etc. One with the new Rx and one with a "regular" Rx. Set them on a card table or something and start walking away with the Tx. And see which one losses signal first. You might be surprised. Case in point, my Hitek
555 has double the ground range of any of my Futabas. So guess which one I use the most?Just food for thought!
Chuck
Uh...sort of.
As Roy Smith said in rec.boats, about 10-15 years ago when GPS units cost $2000, and lots of people were giving very good reasons why they'd never EVER be less than $1000, "anything made of silicon will someday cost five dollars." You still can't buy a $5 GPS, but that's because a lot of it's not silicon; the rubber case, the LCD screen, etc, all conspire to keep the price about $90 at a minimum (but the FEATURE set has increased amazingly). On the other hand, GPS modules to interface to a computer (Like the Laissen iQ 12-Channel) are selling for $60. That should help put an upper bound on a reasonable price for an RC receiver, I think.
--John
A decade or so ago, our club (southern NJ) was receiving complaints from folks over a quarter a mile away from our field. They claimed that large models were flying out well beyond their houses.
I happened to be driving to the field one day when I noticed one of my friends giant scale models buzzing merrily along nice and level at about 150 feet of altitude. He was nearly a quarter mile beyond the houses that were complaining. I would not have believed it if I hadn't seen it with my own eyes.
Naturally, when I got to the field, I talked with my friend about it. He did not believe me. Since this was a serious issue and a threat to the security of keeping our flying field, it was brought up at the next meeting. Still, the guilty parties would not believe what they were being told. After all, they didn't need prescription lenses and those of us reporting the facts did.
A day was set up and "trusted" members of the club were sent out with Radio Shack 49 MHz headsets, while one headset remained for the pilotcopilot to use. They confirmed what several of us had been saying.
World Engines used to sell a radio line named Blue Max in the very early seventies. The Tx output power was advertised as 125 mw. I never had an issue with the range of that 72 MHz set up.
In the old days, we used to remove our Tx antennas to perform a range check. If you got over 15 feet of solid control on the ground (with some radios), it was okay to fly.
Radio range increases significantly as the model rises above the ground. The higher the angle of elevation that the model is to the Tx, the better the signal strength.
Ed Cregger
Why I've seen a miniscule three watts go 23,000 miles without a hitch. On what frequency? You're talking "skip", which is unsuitable for R/C.
they seem to pretty well cover the full spectrum between .1W and a full Watt (from the factory). I'll bet not. Our radios are limited by the FCC to 500 mW.
Hitek 555 has double the ground range of any of my Futabas. If you mean Hitec, yes, they usually have more range than Futaba.
Dr.1
| Why I've seen a miniscule three watts go 23,000 miles without a hitch. | On what frequency? You're talking "skip", which is unsuitable for R/C.
Not only that, but the antennas involved are probably longer than one meter each, and probably have higher gain than a simple whip. And the receiver probably doesn't weigh one ounce.
And 23,000 miles means it's 1,000 miles the other way -- (we are talking about terrestial communications, right?) Hopefully somebody made sure they weren't picking up the signal from the short path ...
And I'll bet there were a lot of `hitches' before it actually worked. QRP is neat when it works, but it's not always easy to make it work.
If you want to talk about weak signals being received, look at the signal from the Voyager 2 probe -- it's billions (8 billion?) of miles away now, transmitting with only a few watts (13 watts originally, may be lower now), and we're still picking it up.
| they seem to pretty well cover the full spectrum between .1W and a full | Watt (from the factory). | I'll bet not. Our radios are limited by the FCC to 500 mW.
Actually, it's 750 mW.
95.210 (R/C Rule 10) How much power may I use?Channel Transmitter power(carrier power)(watts)
... 72-76 Mhz...........................0.75 .....
(from
(Not that I don't agree with you there, just correcting a minor error.)
Why I've seen a miniscule three watts go 23,000 miles without a hitch.
Actually, less power than this has gone several billion miles from Voyager as it boldly goes where no man has gone before. :o)
Like you said, LARGE models. Like I said, 40 size trainer. Big difference when it comes to visual acuity. And how do you know the houses were more than a quarter mile away? Did anyone measure it with something other than the odometer in their car?
Not saying it's not possible having taken sailplanes to a mile up and more. Just saying it's not as common as some would have you believe.
I have 20/10 uncorrected. Which is why I can fly farther away than most.
Built two myself. Nice units for the time. Local Ham helped me tweek them. Never any problems with either radio. Bit one has to admit, the RF environment was a lot cleaner then too. Especially around 72!
Yep! Unplugged many an antenna. Of course, back then you wouldn't burn up the final by pulling the stick either. Not so with some of todays radios.
For a variety of reasons!
Not quite, I'm talking satellite. 23 k up and another 23 k back. Point is, it was three watts line of site. Granted, the freq was different but considering the distance, impressive just the same.
Haven't checked of late but I seem to recall some putting out .750.
Yea! HiteC. Spell check failed again!
OK guys! Just for the record, geosync comm satellites are 23,000 miles up more or less. It's not skip and depending on ones perspective it may or may not be considered terrestial. (well, it does go up and come back)
Not the point! Point is the range can be achieved and the price isn't always power out. Receiver sensitivity plays a big part too.
QRP has been in use by the military for at least 30 years now. Reliably and routinly!
Voyager is a single vehicle. Not the norm! But considering the time of launch, etc., housekeeping data and such is probably UHF. And not exactly high data rates either. Not surprising it can still be heard. UHF receivers of today outperform those of Voyagers time by a long shot. Cleaner and far less complicated too. I wouldn't be surprise to hear of a decent long wire antenna picking up the signals. Actully, the surprising thing is that it's still transmitting!
Yes! It is quite amazing! Before going into Biotechnology I worked in the printed circuit board industry I saw photographs and cross sections of circuit boards used in the Apollo and similar missions. Printed circuit boards were in their infancy and it was amazing how crappy they were. The circuits used then wouldn't pass QC for a $0.99 throw away Happy Meal Whatchamahoozit.
Carl
Lots of one-off circuit boards were made using retail hobbyist etching kits that were sold by Radio Shack and other, similar, companies. It wouldn't surprise me if that is what you were looking at.
Ed Cregger
No. These were actual photos of the circuit boards used on the Apollo missions. The point of having the photos around was to show new engineers (today) what various defects looked like. Even though these panels passed QC checks then, they would be rejected today. The technology has come a long way.
I guess to be more accurate, the photos were of coupons cut from the panels used to make the boards for various launch vehicles. Obviously there was a lot of destructive QC going on for these critical applications.
You know what? I'm thinking of the amateur satellites, I'll bet.
Are you an engineer, Carl?
Ed Cregger
It is interesting to see how far things have come. I was once told how much solder was in an Apollo capsule. I don't recall the number other than it was a seemingly ridiculous amount. Today we'd do it with a fraction of the same amount.
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