* THE FORUM FOR ALL THOSE INTERESTED IN BUILDING AND OPERATING MODEL SUBMARINES *



Join the AMS - Registered Forum users can become members of the AMS and it's free ...... To join register on the forum first then follow the forum link to our membership form which is on our website


For further details of any events shown here also see the "Shows and Events" section on the forum

Thanks for notification of events and keep 'em coming!

.

, Papplewick pumping station, Nottingham, 21,22 April
Bournville June 2nd 2019, 10am
.

. ,

Norwich MBC Submariners joint Model Boat weekend - 27/28th July

Grantham MBC, SUN, AUG 11 AT 10 AM
.
.Model Boat Convention (Exhibition), 24,25 August

.

. Bournville Dive-In (2) MBC, 15th September

,,,,

Barrow in Furness MBC regatta and submarine event, Sunday 22nd Sept 2019,10am

Who is online?

In total there is 1 user online :: 0 Registered, 0 Hidden and 1 Guest :: 1 Bot

None


Most users ever online was 37 on Sun Mar 13, 2011 11:27 am

Latest topics

» Assembling the excellent Scale Shipyards 1/96 SSBN, USS Daniel Webster
Crystal switching? EmptyToday at 2:04 am by merriman

» Eden Dynamic WTC
Crystal switching? EmptyFri Apr 19, 2019 3:20 pm by Deepdive

» John Lambert Plans
Crystal switching? EmptyMon Apr 15, 2019 2:27 pm by david f

» Telemetry on openLRS
Crystal switching? EmptyMon Apr 15, 2019 2:23 pm by david f

» Assisting with a 1/96 NOVEMBER class kit
Crystal switching? EmptyWed Apr 03, 2019 12:36 pm by merriman

» trimming 1/96 USS ALBACORE
Crystal switching? EmptySat Mar 23, 2019 12:37 am by merriman

» Arduino proportional control of a piston tank
Crystal switching? EmptyFri Mar 22, 2019 2:37 pm by tsenecal

» Piston Ballast Systems
Crystal switching? EmptyWed Mar 20, 2019 12:16 am by merriman

» Wayback Machine - We are on it.
Crystal switching? EmptySat Mar 09, 2019 11:29 am by david f

Statistics

Our users have posted a total of 10823 messages in 1773 subjects

We have 803 registered users

The newest registered user is yangshexiang

    Crystal switching?

    avatar
    Tom(ADMIN)
    AMS Forum Owner

    Posts : 2996
    Join date : 2010-11-05
    Age : 59
    Location : Nevada, USA

    Crystal switching? Empty Crystal switching?

    Post  Tom(ADMIN) on Tue Jan 17, 2012 10:40 am

    Can anyone tell me, is it possible to fit some sort of device to my Robbe F-14 tx to allow me to switch between crystals without having to physically remove the back case, remove crystal 1 and replace it with crystal 2?

    I use the F-14 with crystal 1 on my Neptune and crystal 2 on my Deep Quest submersible, and it would be much easier just to be able to flick a switch to change over.
    Hermann
    Hermann
    AMS member

    Posts : 107
    Join date : 2011-07-03
    Location : at home, near Bremen (Germany)

    Crystal switching? Empty Re: Crystal switching?

    Post  Hermann on Tue Jan 17, 2012 8:35 pm

    Hello Richard,

    although crystal switching seems to be simple in imagination (arranging a bank of different crystals and getting access to a selected one via a (e.g. rotating) switch) it is not simple in practice. The reason is that additional devices like a switch will increase parasistic elements (e.g. stray capacitances and parasistic inductivities caused by the expanded wiring) will have an effect to your oscillator circuitry and will probably shift the transmitting frequency a little so that it may not fit any more to the receiver tuning frequency of the specific channel. Stray capacitances in the range of some 10 picofarads can already have an effect and they must be expected with common mechanical switches. So an extreme compact and concentrated switch arrangement would be required
    Another method would be the use of semiconductor switches (pin diodes) directly attached to the crystals and operated with a DC bias voltage decoupled via low pass filter decoupling/ RF blocking. In this case a switch of even more dimensions may be possible as it will only be used to switch the DC-bias for the diode control.
    Of course implementation of crystal switching will require some measurement equipment (e.g. frequency counter, spectrum analyser) to measure the effects on the oscillator circuitry and to prove proper operation.

    I am sure that our electronic specialist John will confirm this. Probably he will give you more practical hints and perhaps even practical help.

    Kind regards
    Hermann


    Last edited by Hermann on Tue Jan 17, 2012 8:36 pm; edited 1 time in total (Reason for editing : adding a missing paranthesis)
    avatar
    Tom(ADMIN)
    AMS Forum Owner

    Posts : 2996
    Join date : 2010-11-05
    Age : 59
    Location : Nevada, USA

    Crystal switching? Empty Re: Crystal switching?

    Post  Tom(ADMIN) on Tue Jan 17, 2012 9:26 pm

    Hermann...I thank you for the explanation.

    But...I have no idea what it all means! I'm totally and utterly confused by it all...by thank you for taking the time to answer anyway.

    I now have a headache.... :-)


    Regards,


    Richard.
    Hermann
    Hermann
    AMS member

    Posts : 107
    Join date : 2011-07-03
    Location : at home, near Bremen (Germany)

    Crystal switching? Empty Re: Crystal switching?

    Post  Hermann on Thu Jan 19, 2012 4:43 pm

    Sorry Richard,

    I didn't want to cause confusion so I hope the headaches will vanish soon.

    Let me give a more simple explanation: If you install more components within the oscillator circuitry of your transmitter (that is the section that controls the frequency of your transmitter) then the transmitting frequency may be shifted (detuned) a little due to "parasistic" effects. As a result transmitter and receiver don't match any more completely and the control range can be much less (or control may even fail).

    Kind regards
    Hermann
    avatar
    Tom(ADMIN)
    AMS Forum Owner

    Posts : 2996
    Join date : 2010-11-05
    Age : 59
    Location : Nevada, USA

    Crystal switching? Empty Re: Crystal switching?

    Post  Tom(ADMIN) on Fri Jan 20, 2012 9:08 am

    Hello Hermann,

    All is well now, the headaches have vanished...

    I don't know why it never occurred to me earlier, but all I need to do is to fit both subs with the same frequency crystal, that way the transmitter will be able to operate either boat without ever needing to open the back case.

    Simples!


    Richard
    Hermann
    Hermann
    AMS member

    Posts : 107
    Join date : 2011-07-03
    Location : at home, near Bremen (Germany)

    Crystal switching? Empty Re: Crystal switching?

    Post  Hermann on Sat Jan 21, 2012 4:30 pm

    Well Richard,

    just as Joe Cocker sings: "...the best things of life, are the simple things..."


    Best regards
    Hermann

      Current date/time is Tue Apr 23, 2019 4:55 am