Wondering if any other fliers are having big "hits" with their E7 especially QPCM.
Since we bought 2 of them on 36.41/36.43 mhz, we have done nothing but lose planes. There are now 4 of us in our club experiencing similar probs. Basically takes off no problem, flies for a while then says goodbye to its maker. We are all experienced fliers, so metal contact, antenna loc. etc already considered
We have tried several different rec's in 6 or more planes with same results. Needless to say we are losing $$ at a rapid rate. Both sets we bought (QPCM) have been back to model engines in Victoria twice. Retuned (1) first time then stated no probs the other times.
We are needless to say getting very frustrated. JR and FUTABA radios on these frequencies are not getting any problems apart from the occasional glitch.
We are talking full servo deflection here or full lock out in case of Qpcm.
Any help or advice would be greatly appreciated.
Thank you
JA.

How much range do you get when testing with the aerial down?

Sounds suspiciously like a 40Mhz set that someone's tried to "pull" down to 36Mhz by retuning and, as a result, is suffering low receiver sensitivity.

Band-changing (as opposed to intra-band frequency changing) can be quite a complex operation and unless it's done very carefully you can end up with all sorts of odd things going on -- such as oscilators running at the wrong crystal overtone, etc. Such mistakes can produce a set that works on the bench-- but which is unstable or which has very limited range once tossed into the air.

Yes I'm getting not very good range, and big hits with my QPCM. Its on 36.250
Using QPCM receiver or PPM receiver, range is around 5 meters,(pretty scary).
All of my other radios when used have around 30-50 meters range with arial in.

I should also add that I have flown with the radio and it seemed to work okay.
Just compared to my flash 5 radio, it, the Eclipse QPCM doesnt seem to have the same range with arial down.
However the range does improve when I use it on one of my planes that doesnt have digital servos in it!, maybe its the digitals?
Good luck with it.

Thanks for replies.
XJET- it really seems like you know your stuff! although i am only a layman with respect to ppm/pcm tech. We really need help to pin the source and get somebody to admit something is wrong here, how can i back this up? We dont want our planes replaced, just dont want to lose anymore !
SMOOTHPASS- "ditto" This is exactly what we are experiencing. To this day my old trusty focus 4 outdoes range check on Eclipse every time!

I am getting about 40 paces "thumb high" range check, even taxiing entire runway to no avail once airborne. We do have a "corridor of death" as such were you can expect the occasional hit flying in or out of the "corridor".
Wonder if there is some sort of interference specific to hitec and not others.?
I really dont want to just go out and buy a JR or FUTABA, none of us would be comfortable with selling our "problem" to somebody else. I like to think i sleep well at night.
thank you

I too am getting big hits with my E7 at around 100ft while flying, on 40mhz PPM rather than QPCM. All 3 of my superslim7 rxs on the 40mhz band are affected, all in different airframes (foam slope gliders!!). I've tried new tx and rx xtls, changing channels from 485 to 451 to 465, with no improvement, I even change flying sites to see if the problem is local......nope. A fellow pilot switched to Futaba after he felt it was his E7 that killed his Sig extra due to limited or no response at moderate range of 200ft, all other causes were checked out such as battery pack, switch harness, push rods, other txs at the site, etc.
I have several indoor helis which so far seem ok with their SS7 rxs and the E7 (max flying range thou is only 30-50ft away), however my confidence in the radio is gone.

I'll be buying Futaba from now on.

Mossie, what servos are you using, what type/capacity of receiver battery do you have, and were you flying alone when you noticed these "hits"?

Hi Xjet.

Most of the time I am flying alone. It makes little difference if other TXs are around or not.

First model is a 2 ch JW foamy with a SS7(no1) 485 xtl pair of ty1 05057MG micro servos, 5cell 600SCR rx pack. Limited range with this model, maybe 250 ft max.

Next glitcher is a 4ch 60" foam racer with 2xhs81MG wing servos and 2xGWS naros with SS7(no2) on 451 with a 4cell 720nimh pack.
Almost unflyable with a 100ft range.

Next on the list is a Spirt Elite 2m balsa ship, SS7(no3) on 485. 6xhs81MG servos, golden rod pushrods, 4cell 600mah sanyo pack.
Almost unflyable with a 100ft range.

When I first got this Tx I had little or no glitches with other foam models using these rxs. The major problems started with the Elite which was always a little glitchy but got worse over time. Since then things have been quite bad. I had the radio checked out and tuned once, no improvement. Had the rxs checked and tuned, no improvement.
Changed ALL of my xtals for no improvement. Swapped tx antenna for new one, even tryed rubber ducky. No improvement.

I do have more success when using GWS naro receivers.

I have had several experienced flyers look at my models and the radio installations, no faults found.

Hitec have tried to help but the gremlin still exists.

edit: I should add that I thought I had solved the problem in the 60"racer when I removed the aileron extension wires. The model range checked out ok but problem returned upon moving to the flying site.

Is there anyone flying on the same frequency as you who has a different (non-Hitec) receiver so that you can try yoru transmitter with their flight pack?

If you can determine whether it's the receivers or transmitter then that's half the battle.

You say you get better results with the GWS receiver -- how much better?

Sounds like you have range problem, more likely than not based on your comments the TX maybe the problem. Why not return it to Hitec Service for evaluation. Be sure and include the TX modules in use, I would also send in the RX's if possible. Better safe than sorry.

You mention "almost unflyable with a 100' range". Antenna down range check or?

It is going back again this week. I already sent it away once with 2 of the rxs.

the antenna is fully extended, still only 100ft range.

Im thinking of swapping to 72mhz anyhow so that may help.

I have tryed futuba rxs in place of the rx and things improved a little but still glitchy with limited range.

For some reason the gws rx seem to have the least glitches and the greatest range. I dont know why. They still arent perfect, but without doubt the best so far.

You might be interested in the receiver shoot-out I'm doing at the moment in which I'm comparing as many of the current crop of RC receivers as I can, measuring performance in a number of important areas such as noise-rejection, sensitivity, cross-mod/inter-mod, etc.

It will be interesting to see how the universally praised Hitec gear compares to offerings from the likes of FMA.

As for going to 72Mhz, I've got an Eclipse 7 with the Spectra module which I use with a Hitec Supreme and Hitec 555 receivers. So far I've had no problems at all -- except I'm going to have to upgrade the transmitter batteries to NiMh because the standard 600mAh Nicads are pittiful.

Moosie

Is the service center in New Zealand; in any case is it an approved service center or a Hitec facility?

You HAVE a range problem if your experiencing problems at 100' with the antenna extended.

Did you purchase this set new? Has it been retuned, crystals changed out, RX's originally manufactured for the frequency and or band used in your world. Do the RX's you have tried other than Hitec products require retuning with crystals change outs? Are these all Dual Conversion RX's with the appropriate crystals? Are you changing out the TX module when changing out frequencies? Are you using a Spectra module?

Its an approved facility. I bought the TX new. After some problems came up I sent the TX back to be checked out and upgrade the software and hardware to the QPCM version while it was there. Unit came back upgraded with a clean bill of health.
It has never been moved off its original 40mhz. I have of course often changed xtals in the 40mhz band but the module is a standard supplied 40mhz unit. The tx xtals have always been hitec and came direct from the supplier new in their bag.

All of the other rxs I have tried have been Dual Conversion except for the GWS ones. All the xtals in these rxs are of matching brand, within the original range (ie 40mhz) and are dual conversion xtals (except once again the GWS units).

Update:

I have just had a local Futaba design technician (recommended by some flying buddies) who said the 2x SS7 rxs were miles out in their tuning (I have never touched them internally) and the TXs output was well down.
With this information I am sending the whole lot back to Hitec to check again. I dont expect this to be covered under any warranty, I will happily pay for anything that needs to be done. I just want a reliable radio.
If they cant find any problems to fix this time they can keep it.

If you're really stuck then drop me a line. I've got over 30 years in analog and digital electronics and have been working on RC gear since the early 1970's -- just a couple of months ago I offered to act as an NZ service facility for Hitec here -- they never responded to that offer :-(

Seems we are all suffering same problem. All our hits occur at approx 100ft+, regardless of s/c, d/c or pcm rec's. Everything seems to point to the radio.
As i said earlier sending the 2 units back twice to model engines(the importer), and repeated scanning of the field has resulted in no difference.
Most of what weve tried is original hitec equip with original crystals, usually straight out of the complete flypack. Frequency is making no difference at all.
Worst part is we all love the feel and programming of these radios, as Mossie said we just want them reliable.
We are losing members, and word is ... Dont buy hitec!! Surely this is going to lose retailers business? Bad news travels fast, as we know.
I am also flying heli's still with radio, but theres no way i'm going to do circuits until problem is found.
Also found (as smoothpass stated), digital servos intensifies problems. Why do we get lots of sevo jitter using 525bb/645mg/9525 servo's but not 422's? Tried 1100+1500mah packs(4.8 & 6v), no difference.
X-JET, would love to know results of your shoot out. Next we are going to try jr. vs. hitec on same model.

One thing to note is changing the crystals in the TX module is not an approved procedure, at least not here in the US. The module is tuned to the specific crystal in use; this may contribute to your reduced range. Additionally I am not familiar with the SS7 RX's, these may in fact require retuning as well. However if these RX's are like most offered by Hitec this is not a problem.

Sounds like the radio tech you mentioned put your equipment on the bench and did some tests. His evaluation of same makes sense based on the problems you’re experiencing.

It's not unknown for receivers to exhibit instability which is dependent on the signal strength being received. Sometimes this can even be caused by bad tuning or a clumbsy band-change modification.

That instability *could* be exacerbated by electrically noisy servos or those which draw sufficient current to cuase a slight sag in the receiver voltage.

When faced with these symptoms a tech should use an RF signal generator to vary the RF signal from 1uV or so, right up to 100mV or more -- watching for signs of instability along the way.

It would also pay to check the transmitter output with a spectrum analyser, just to make sure that all its RF is coming out at the desired frequency -- botched band-conversion jobs can sometimes produce inordinate amounts of second and even third-harmonic output -- and I've even seen them opperating at the first subharmonic.

I'm still wondering whether the 36Mhz sets are "retuned" 40Mhz units or whether they're designed for 36Mhz operation right from the start.

I am thinking of getting a replacment TX module for my E7 to try out before I send it back. I will get another 40mhz one on the freq I use most. I am correct in thinking all of the transmitting work is done in this module? As I understand it the rest of the radio has no effect on RF output?

Xjet, I think I would like you to have a look rather than Hitec. They didnt find anything before so may not find anything this time. As I said above I will be trying a new module first.

You can email me direct at mossie@inet_co_nz and we can swap some contact details.

Cheers

That email address bounced when I tried it (yes, I used [email protected])

oops. try mossie@inet_net_nz

Hi Xjet
I would love to see your findings with mossies radio too.

I have ordered a new 40mhz RF module and a new antenna cos they were both cheap as chips. Also I have cycled the tx battery a few times on my Orbit to check discharge capablity.
I have a new aerial for a SS7 rx that I will test things with just to make sure it has no internal breaks or anything silly.
If these thing dont help its off to Xjet.

Sean

please let us know if it makes any difference Mossie.
XJET- i spoke to retailer(not importer), he seems to feel they were uptuned from 35mhz, not down from 40? He also wants to get to the bottom of this, bad for business and all that.
Thank you