nigel newby Posted November 28, 2018 Share Posted November 28, 2018 Is there a difference between aircraft, and helicopter crystals. I have a pair of crystals channel 61 35mhz and they were advertised as helicopter crystals, yet the transmit crystal work ok with my other ch 61 rx crystals. Nigel N Quote Link to comment Share on other sites More sharing options...
CARPERFECT Posted November 28, 2018 Share Posted November 28, 2018 Simple answer is. NONE Quote Link to comment Share on other sites More sharing options...
nigel newby Posted November 28, 2018 Author Share Posted November 28, 2018 Thanks for that I thought so. I also love simple answers Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted November 28, 2018 Share Posted November 28, 2018 However, on 35 MHz, there is a BIG difference between different manufacturers transmitter crystals (for example JR and Futaba - to name but two!). Only use the manufacturers crystals in transmitters. -- Pete Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 28, 2018 Share Posted November 28, 2018 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
nigel newby Posted November 28, 2018 Author Share Posted November 28, 2018 OK chaps, I am using a Futaba system Here are the make of crystals I will be using. Can you tell me the make, and are they OK. Cheers Nigel N Quote Link to comment Share on other sites More sharing options...
John Tee Posted November 28, 2018 Share Posted November 28, 2018 Which Rx are you using? could be single or dual conversion as above - need the right ones John Quote Link to comment Share on other sites More sharing options...
nigel newby Posted November 28, 2018 Author Share Posted November 28, 2018 I have both types of RX but that should not be a problem as they just receive the signal for that freq. The single/duel receive section is just how the receiver works. You can have a single or duel conversion receiver in your kitchen, but they both pick up radio 4. Nigel N Quote Link to comment Share on other sites More sharing options...
PatMc Posted November 28, 2018 Share Posted November 28, 2018 Not if the radio relies on the correct Xtl for the tuning. A dual conversion Rx needs a dual Xtl, a single conversion Rx needs a single Xtl. The Tx only needs the correct Xtl for that manufacturer.. Edited By PatMc on 28/11/2018 19:54:43 Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted November 28, 2018 Share Posted November 28, 2018 PatMc is exactly right. Receiver crystals are offset from the transmitter frequency by the IF frequency of the receiver. In a single conversion receiver, that is usually 455KHz, and in a double conversion, usually 10.7MHz. Clearly, they are not interchangeable. Some transmitters use crystals that are half the output frequency, and some one third. In addition, because of the FM nature of the signal, the transmitter needs to be aligned to a specific crystal specification. Whilst using a different crystal may allow the transmitter to - er - transmit, there is no guarantee it will be on the right frequency. The crystals in Nigel's photo look like later Futaba types, but also resemble HiTec types. I can't tell from the photo which they are. -- Pete Quote Link to comment Share on other sites More sharing options...
nigel newby Posted November 28, 2018 Author Share Posted November 28, 2018 Sorry chaps got the wrong end of the stick. Yes I would say that the rx crystal is for single conversion. But I do have both so can test it out sometime. But I have also gone on my ic7300 and the appears to be a few hertz difference in tx freq. My Futaba crystal seems to be on 35.010, yet the unknown crystal appears to be transmitting on 35.008. So will not use the unknown one. The pair only cost a couple of quid so rather waste that, than a plane at distance. Unless some knows what tolerance radio control receivers work too. Nigel N Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 29, 2018 Share Posted November 29, 2018 As I understand it if you buy a pair of matched Tx Rx crystals by the same manufacturer they will work regardless of the actual make of the Tx or Rx. I use and still do) an identical pair (single conversion Ch 66 and cheap) to those in your photo with my Futaba Skysport Tx with a Corona rx. If you can physically see the plane then it is within range! I believe Futaba did make their 'own brand' crystals to a fine tolerance and set towards the limit of the particular channel frequency in an effort to ensure their crystals would not work so well if mixed with other brands. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted November 29, 2018 Share Posted November 29, 2018 On crystal frequency Numbers Nigel, When 35mhz was prolific, to avoid any clashes with flying from your patch, and the glider guiders in the hills There was a gentleman's agreement that Gliders used the Even Numbers , and those down below Used Odd Numbers, giving some spacing. It still applies at my place, as many of the lads flying high in the distance, still use 35mhz Quote Link to comment Share on other sites More sharing options...
Charles Smitheman Posted November 29, 2018 Share Posted November 29, 2018 And do a range check of course...... Quote Link to comment Share on other sites More sharing options...
CARPERFECT Posted November 29, 2018 Share Posted November 29, 2018 Nigel, the duel conversion rx requires d/c crystals and the single rx require single ones. the TX crystals are all the same, its just the rx ones that differ, Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted November 29, 2018 Share Posted November 29, 2018 Posted by Simon Chaddock on 29/11/2018 00:17:28: As I understand it if you buy a pair of matched Tx Rx crystals by the same manufacturer they will work regardless of the actual make of the Tx or Rx. Simon, they may work, but they may well not be on the right frequency. For example, JR and Futaba have a different specification. If I put a JR crystal in a transmitter designed for Futaba it is 1) significantly down on power and 2) 5KHz high in frequency! Since channel spacing is only 10 KHz, this is a potentially disastrous situation! In the days when we were all flying AM and using 3rd overtone crystals, yes you could swap crystal with impunity most of the time. But NOT with FM! Nigel: If your transmitter is using PPM (as opposed to PCM), a frequency counter will typically read about 1 KHz or so LOW. This is because the PPM signal is assymetric, and spends more time at the lower end of its FM swing than at the high. Thus on average it will read low. A PCM signal is symmetrical and will read the correct frequency. As well as frequency, it is worth checking the power output with a Field Strength Meter. The meters on some transmitter do register RF output, but many just monitor the battery voltage. You can tell which you have by grabbing hold of a fully extended aerial and seeing if the meter reading drops. If it does, it is measuring RF. If it doesn't, its just a battery monitor. -- Pete Edited By Peter Christy on 29/11/2018 09:18:33 Quote Link to comment Share on other sites More sharing options...
nigel newby Posted November 29, 2018 Author Share Posted November 29, 2018 Fine chaps, yes we use the split freq for gliders and power models. But few go over to the gliding slopes anymore. 20 years ago it was quite busy, but now next to nothing. Also with most on 2.4 ghz nearly all the 35mhz channels are always free. Peter I don't have a freq counter, I am just using my amateur radio transceiver and reading the freq that the futaba is transmitting on. As I said the difference in each crystal is about 2 hertz, so not a lot. I will use the crystals but only as a pair. If they are matched then that should be ok. It would be interesting to check other channel 61 crystals to see just how close they are to there stated freq. My radio control transmitter is a Futaba T6EXAP. Will have to check the book of words on it to see if it has an rf output meter. But according to my IC 7300 they are both putting out the same output. I dares say that they could be futaba crystals, but why no one put there name on them I do not know. Nigel N Quote Link to comment Share on other sites More sharing options...
pete kent Posted November 29, 2018 Share Posted November 29, 2018 Hi guys I have some Dual conversion Futaba crystals if anyone wants some spares There's 12 Rx crystals and 7 Tx Crystals.... Some are pairs but theres also some double up Rx Ch 68 & 61 there's 4 of each Might be couple of HiTec mixed in as well if anyone wants the lot for £5 plus postage? message for details and whats available Quote Link to comment Share on other sites More sharing options...
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