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Hitec Eclipse7 weak in Positive shift mode

Old 06-20-2005, 06:21 PM
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jemke
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Default Hitec Eclipse7 weak in Positive shift mode

I have two(2) New Hitec Eclipse7 transmitters that I intended to use to replace my JR (6108) transmitter and trainer box but I am having a problem with low transmitter output in positive shift mode. Both Hitec transmitters are Eclipse7 with Spectra and they simply will not range check or properly fly matched up to a JR 610m receiver (I have six of these) I use in my electric planes. The JR 6108 transmitter operates these at great distance, almost out of site distance, but the Hitec transmiters looses the planes at about 300 feet. The Hitec Eclipse 7s (both of them) function perfectly well on negative shift receivers like Futaba and Hitec but they seem to loose something when the mode is set to positive shift. Since most of my receivers are JR I am afraid to use the Eclipse transmitters on any of my planes even the 700 receivers even though I have only experience the problem on the JR 610m receivers.

A friend with an Eclipse 7 described the same problem to me with his JR 610m and said he changed to a GWS receiver and the problem was solved. Is there a kown problem with this transmitter receiver combination or with positive shift mode.

Thanks,

Mike Scott
Old 06-21-2005, 11:43 AM
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tohm
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Default RE: Hitec Eclipse7 weak in Positive shift mode

You should get the same range with the Eclipse that you have with the 6108. If you would like to send the Spectra module in for service, we can check the tunning and see if it is where it should be.
Old 06-21-2005, 12:25 PM
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jemke
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Default RE: Hitec Eclipse7 weak in Positive shift mode

I have two Eclipse 7 and two spectra modules and in poling the people in my club which has over two hundred members we have attributed a number of crashes and near crashes to Hitec Eclipse spectra modules when teamed up with JR Positive shift receivers.

These transmiters seem to work just fine with Hitec Futaba or any negative shift receiver but they simply fail when attempting to control a positive shift receiver. We counted five Eclipse tranmitters that were unable to control my 2 meter sail plane with a JR 610M receiver at 300 feet yet my JR 6102 controls it as far as you can see it. I even tried my trainer box JR Quatro and it has the range though not the channels to control the sail plane too.

I am convinced that many of the crashes reported on this forum are from attempts to control positive shift receivers. The Eclipse with spectra just isn't up to the task.

I have a small number of negative shift receivers that I have acquired over the last several years and they seem to work just fine with the Eclipse 7 on range checks but I've decided to ditch these two transmitters on ebay. I have too much invested in my planes to trust a weak signal transmitter.

Mike Scott

Old 06-21-2005, 05:37 PM
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Default RE: Hitec Eclipse7 weak in Positive shift mode

how much for your trans each?
Old 06-22-2005, 12:16 PM
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MikeMayberry
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Default RE: Hitec Eclipse7 weak in Positive shift mode

The Eclipse radio and Spectra module have been sold for many years and there is no indication that this has been a problem. To make a rash decision to "ditch" these transmitters without even allowing our service department to solve the problem for you seems very rash.

To indicate that this is a permiment problem for all Eclipse radios with Spectra modules is completely unfounded; our track record proves that!

Perhaps you could at least give us some consideration and allow us to repair the problem so you can at least sell the systems to someone knowing that they are working the way they should?

Mike.
Old 06-22-2005, 06:26 PM
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jemke
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Default RE: Hitec Eclipse7 weak in Positive shift mode

Of course you are right and it could be that I got two brand new spectra modules that need tuning, but my frustration with the Eclipse 7s was acerbated by a recent visit to my clubs field. A friend there with an Eclipse 7 could not control my JR610M but my JR6102 transmitter functioned flawlessly with this plane. He told me that he has never had any luck with those lousy JR receivers but my experience has been that the JR receivers have worked absolutely glitch free for me. The club has more than 200 members and several of them have Eclipse 7 spectra model transmitters and some of them have had problems controlling positive shift receivers as well. One incident caused the destruction of an Alpha 60 with a JR 700 model receiver. I came home and tested my two new transmitters against all of the different positive shift receiver I own, most of which have worked absolutely glitch free with either JR or Airtronics transmitters. The results were that both Eclipse units simply did not work well in positive shift mode.

I would be more than willing to send in the spectra modules to see if the problem can be fixed and I will do so but for now I have to stop using these transmitters or replace the receivers in my planes with negative shift receiver units. It's a shame because I love the feature rich programming of the Eclipse 7 and I have fiberglassed the handle wells to prevent them from pulling out like they seem to do and one of the units has a rubber duclky glassed into it. The other unit has the standard Hitec antenna and they seem to work exactly the same so I do not think the Rubber Ducky is the problem. Both transmitters fail with both spectra modules at about the same distance regardless of the antenna and both control negative shift receivers at great distance regardless of antenna.

Thanks,

Mike Scott

I will send copies of these emails with the units.
Old 06-22-2005, 08:36 PM
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Default RE: Hitec Eclipse7 weak in Positive shift mode

May I suggest that you try a standard Hitec TX module to validate if the Spectra module is the source of the problem?

As far as I know the shift modulation feature is well ahead of the TX RF module and should have No bearing on the range IMO.

There is always the chance that an OEM compatibility conundrum exists with the Spectra Synth module and JR RX’s. If you’d send one the JR RX’s in with the TX’s and make Tony aware of the suspected problem, he maybe be able to validate or not the source of the TX/RX shortcomings.
Old 06-22-2005, 09:55 PM
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jemke
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Default RE: Hitec Eclipse7 weak in Positive shift mode

In an FM transmitter the frequency of the transmitter is varied positive or negative from the carrier frequency. This must be done in the transmitter module as that is where the carrier is generated.

My guess about the Spectra module, and a possible reason for the problem, is that the base oscillator of the spectra module is likely center tuned to the median frequency of the band. Since all of my receivers are on LOW side channels my guess is that the Spectra module is clipping the low side or positive shift side of the band. To sort of test this theory I tried a positive shift receiver on channel 56 and it seemed to work okay

There is a possibility that they can tune the module so that it does not clip the low positive shift channels. Hopefully this will not have a bad effect on the negative shift receivers on the high end of the band. At least that is my hope. In all the cases, including the ones at the club, the receivers were low band receiver crystals. Although JR and Airtronics do not have low and high band receivers like Futaba and Hitec, all the failures were with channels 17 to 22 positive shift receivers.

We will have to wait and see but I am sending a new JR 610M on a low channel along with the two Spectra Units.


Thanks,

Mike

Old 06-22-2005, 10:16 PM
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Default RE: Hitec Eclipse7 weak in Positive shift mode

Mike

Sounds like you have a feel for the purported problem.... I'm not as well educated technically as I'd like with this synth stuff, but your description of the how and why makes sense anyway.

FWIW: Hitec Rx's are center tuned too...
Old 06-29-2005, 08:36 AM
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Default RE: Hitec Eclipse7 weak in Positive shift mode

Is this an issue I need to worry about with positive shift in general, or is it just with JR receivers? I've just ordered a Hitec Eclipse 7 with the Spectra module and I had planned to use it with my existing Airtronics and GWS positive shift receivers. I just thought it would be nice to be able to use one transmitter with all of my planes, but it's not worth it if this is a potential issue.
Old 06-29-2005, 11:58 AM
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Default RE: Hitec Eclipse7 weak in Positive shift mode

This is not a known issue so I don't think you will have any problems.
Old 06-29-2005, 12:12 PM
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rixkix
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Default RE: Hitec Eclipse7 weak in Positive shift mode

Thanks for the reply - FUD can go a long way when you're trusting your equipment to a product you're unfamiliar with.
Old 06-29-2005, 09:44 PM
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Default RE: Hitec Eclipse7 weak in Positive shift mode

Mike

Did you have knowledge of the performance of low band RX’s other than the JR’s? Hitec, Airtronic’s or others, do they work OK with the Spectra module?

Was a standard TX module employed for testing?

A little research has lead me to the following understandings:

My previous comment on “shift selection” mode being well ahead of the Spectra module, any module for that matter is accurate; it’s done board level of the TX. The feature will work with a standard or Spectra module and it has no bearing on range. That said I concur with your comment on the origin of the carrier frequency and or the modulation shift in play. If the TX module is not producing accurate on channel/frequency carrier waves reduced range is likely, however I don’t see the relationship with Negative or Positive shift carriers being a factor. What am I missing?

All output frequencies are exact proportions (or should be) of the reference frequency (channel 35 in the case of the Spectra), digital dividers make this possible. The design attributes of these devices suggests that if there was a problem off center or tune it would remain the same for any base frequency selected regardless of shift orientation. A frequency counter will tell the tale IMO.

Assuming all is within specification of the TX module and the subsequent carrier wave and the problem is prevalent with a specific RX or RX brand for that matter, it maybe possible that the discriminator of the RX that converts frequency to voltage is not accurately matched to the range of frequencies generated in the modulator. Additionally if the pass-band of the RX is short any of these “frequencies” were back to square one.

Hitec Service assured me the range or integration problem your experiencing is uncommon and was confident they could work it out with fine tuning the Spectra module to your equipment needs.

We've seen many circumstances to date with different OEM radio equipment suppliers and aftermarket equipment suppliers too, that simply experience problems with others synthesized TX modules and their specific RX's. Integrating alternate OEM equipment witihin to one another has no guarantees. A fellow modeler suggests there is a defacto standard that OEM's endeavor to work within, problem is they don't share information I suspect.

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