Xtal Help Needed...... - UK Vintage Radio Repair and Restoration Discussion Forum

Wayne jzt · 2nd Jun 2009, 7:55 pm

I have just purchased a FDK MULTI-U11 70cm radio...
It seems that the Xtals have just been put in the radio any old how?
Transmit and Receive are all over the place...I would like to know if there is any where here in the UK to get hold of these Xtals ?

They are of HC-25U plug in type,.....is there a equivalent Type?There are two channels that are near there as in transmitting on 433.450...and the RX is on 433.425. This set requires both Transmit and receive Xtals... I know nothing of this type of radio..all mine are Valve! Any help would be much aprecaited...

Thanks
Wayne

Boom · 2nd Jun 2009, 8:08 pm

I don't know the set either but I'd be careful before messing about. It might well have a PLL so the Xtals might not make sense at first glance if you are used to third harmonic transmitters.

Wayne jzt · 2nd Jun 2009, 8:10 pm

Also the chan that is Transmitting on 433.450 and Receiving on 433.425,...on the TX Xtal had 433.50 and the same on the RX Xtall....but my feelings are that just any Xtal has been put in the radio prior to me buying it,...not a lot was paid,..all it was purchased for, was to talk to a good pall on 433-475 and the call freq...I would still be lost on the TX and RX Xtal for each channal...or freq...Help !

Sean Williams · 2nd Jun 2009, 8:41 pm

Hi Wayne,

Ah, yes a problem indeed!

However, fairly easy to work out.

Take one of the crystals out of its socket (use the transmit one that is for 433.450)

Read the frequency off the crystal - probably 8.000something......

Divide 433.450 by that crystal frequency and this will give you the transmit multplication factor - probably x24 or something like that - you can then use this to work out what frequency tx crystal you need.

RX is a little trickier

Assuming the IF (intermediate frequency) is 21.4Mhz (this is usual for 70cm gear), you need to either add or subtract this from the actual recieve frequency, and then divide the resulting number by the crystal frequency - if you do not get a whole number or very close to one then you need to subtract the IF, or add it depending on what you did the first time.

If the IF is 10.7Mhz, rare, but not unheard of... then you need to subtract or add this to your calculations (be aware that the RX might be dual conversion, so might have both IF frequencies - in this case always use the hihest frequency)

You can order crystals from Quartslab - google them - they are really helpful!

HTH
Sean

Wayne jzt · 2nd Jun 2009, 9:14 pm

Thanks Sean,.,.

All that is marked on the Crystals are the freq nothing else as in 433-450 and so on...
There are no frequency of the crystal marked...

The method I used is as follows....

Transmition..... = F Div 24(MHz)
Reception....... =(F - 397.7) Div 3(MHz)

If I worked this out correct... lets say for Transmit and Receive on lets say 433.500.

= F Div 24 (MHz) = 18.0625
= ( F - 397.7 ) Div 3 (MHZ) = 11.9333

Would this mean I would need a Transmitting Crystal at 18.0625
and a Receive Crystal at 11.9333...

Sorry id this is not correct as maths is not a strong point my side...Thanks

Sean Williams · 2nd Jun 2009, 9:44 pm

Wayne,

did you take the multiplier details from a manual?

the tx sounds about right, not so sure about the rx though - /3 isnt really enough for an FM set

Wayne jzt · 2nd Jun 2009, 9:48 pm

Transmition..... = F Div 24(MHz)
Reception....... =(F - 397.7) Div 3(MHz).....
Should have said used not use...

Its in the manual for the radio?
No wonder I got it cheap ...

Sean Williams · 2nd Jun 2009, 10:32 pm

This might help - if you look at the schematic it gives the multipliers for the tx and rx

Wayne jzt · 4th Jun 2009, 5:29 am

I came across this one...for 70cm

For T1 bands sets
RX Crystal frquency - (RX Freq + 21.4)/8
TX Crystal frequency - (TX freq)/32

For U0 bands sets
RX Crystal frequency - (RX freq - 21.4)/8
TX Crystal frequency - (TX freq)/32

Does this seem more like it? also What does the T1 band and the U0 band mean?

Sorry but I did say that the Crystal side of things is new to me...Cheers

Wayne

Sean Williams · 4th Jun 2009, 7:33 am

Wayne,

That looks suspiciously like the mult instructions for Pye PMR gear - this will not work for you.

Look at the info I posted above - you should have your answer there.

Or try ringing Quartslab up - they might be able to calculate the frequencies for you - they hold a lot of information - give them the details of the radio and then see what they can do.

Cheers
Sean

Wayne jzt · 4th Jun 2009, 12:58 pm

Thanks Sean I have contacted Quartslab and they have the list for this radio so all is in order....many thanks for your replies,...

2nd Jun 2009, 7:55 pm	#1
Wayne jzt Retired Dormant Member Join Date: May 2009 Location: Doncaster Posts: 9	Xtal Help Needed...... I have just purchased a FDK MULTI-U11 70cm radio... It seems that the Xtals have just been put in the radio any old how? Transmit and Receive are all over the place...I would like to know if there is any where here in the UK to get hold of these Xtals ? They are of HC-25U plug in type,.....is there a equivalent Type?There are two channels that are near there as in transmitting on 433.450...and the RX is on 433.425. This set requires both Transmit and receive Xtals... I know nothing of this type of radio..all mine are Valve! Any help would be much aprecaited... Thanks Wayne

2nd Jun 2009, 8:08 pm	#2
Boom Retired Dormant Member Join Date: Jan 2007 Location: Westbury, Wiltshire, UK. Posts: 2,451	Re: Xtal Help Needed...... I don't know the set either but I'd be careful before messing about. It might well have a PLL so the Xtals might not make sense at first glance if you are used to third harmonic transmitters.

2nd Jun 2009, 8:10 pm	#3
Wayne jzt Retired Dormant Member Join Date: May 2009 Location: Doncaster Posts: 9	Re: Xtal Help Needed...... Also the chan that is Transmitting on 433.450 and Receiving on 433.425,...on the TX Xtal had 433.50 and the same on the RX Xtall....but my feelings are that just any Xtal has been put in the radio prior to me buying it,...not a lot was paid,..all it was purchased for, was to talk to a good pall on 433-475 and the call freq...I would still be lost on the TX and RX Xtal for each channal...or freq...Help !

2nd Jun 2009, 8:41 pm	#4
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,518	Re: Xtal Help Needed...... Hi Wayne, Ah, yes a problem indeed! However, fairly easy to work out. Take one of the crystals out of its socket (use the transmit one that is for 433.450) Read the frequency off the crystal - probably 8.000something...... Divide 433.450 by that crystal frequency and this will give you the transmit multplication factor - probably x24 or something like that - you can then use this to work out what frequency tx crystal you need. RX is a little trickier Assuming the IF (intermediate frequency) is 21.4Mhz (this is usual for 70cm gear), you need to either add or subtract this from the actual recieve frequency, and then divide the resulting number by the crystal frequency - if you do not get a whole number or very close to one then you need to subtract the IF, or add it depending on what you did the first time. If the IF is 10.7Mhz, rare, but not unheard of... then you need to subtract or add this to your calculations (be aware that the RX might be dual conversion, so might have both IF frequencies - in this case always use the hihest frequency) You can order crystals from Quartslab - google them - they are really helpful! HTH Sean __________________ Engineers make things work and have spare bits when finished

2nd Jun 2009, 9:14 pm	#5
Wayne jzt Retired Dormant Member Join Date: May 2009 Location: Doncaster Posts: 9	Re: Xtal Help Needed...... Thanks Sean,.,. All that is marked on the Crystals are the freq nothing else as in 433-450 and so on... There are no frequency of the crystal marked... The method I used is as follows.... Transmition..... = F Div 24(MHz) Reception....... =(F - 397.7) Div 3(MHz) If I worked this out correct... lets say for Transmit and Receive on lets say 433.500. = F Div 24 (MHz) = 18.0625 = ( F - 397.7 ) Div 3 (MHZ) = 11.9333 Would this mean I would need a Transmitting Crystal at 18.0625 and a Receive Crystal at 11.9333... Sorry id this is not correct as maths is not a strong point my side...Thanks

2nd Jun 2009, 9:44 pm	#6
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,518	Re: Xtal Help Needed...... Wayne, did you take the multiplier details from a manual? the tx sounds about right, not so sure about the rx though - /3 isnt really enough for an FM set __________________ Engineers make things work and have spare bits when finished

2nd Jun 2009, 9:48 pm	#7
Wayne jzt Retired Dormant Member Join Date: May 2009 Location: Doncaster Posts: 9	Re: Xtal Help Needed...... Transmition..... = F Div 24(MHz) Reception....... =(F - 397.7) Div 3(MHz)..... Should have said used not use... Its in the manual for the radio? No wonder I got it cheap ...

4th Jun 2009, 5:29 am	#9
Wayne jzt Retired Dormant Member Join Date: May 2009 Location: Doncaster Posts: 9	Re: Xtal Help Needed...... I came across this one...for 70cm For T1 bands sets RX Crystal frquency - (RX Freq + 21.4)/8 TX Crystal frequency - (TX freq)/32 For U0 bands sets RX Crystal frequency - (RX freq - 21.4)/8 TX Crystal frequency - (TX freq)/32 Does this seem more like it? also What does the T1 band and the U0 band mean? Sorry but I did say that the Crystal side of things is new to me...Cheers Wayne

4th Jun 2009, 7:33 am	#10
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,518	Re: Xtal Help Needed...... Wayne, That looks suspiciously like the mult instructions for Pye PMR gear - this will not work for you. Look at the info I posted above - you should have your answer there. Or try ringing Quartslab up - they might be able to calculate the frequencies for you - they hold a lot of information - give them the details of the radio and then see what they can do. Cheers Sean __________________ Engineers make things work and have spare bits when finished

4th Jun 2009, 12:58 pm	#11
Wayne jzt Retired Dormant Member Join Date: May 2009 Location: Doncaster Posts: 9	Re: Xtal Help Needed...... Thanks Sean I have contacted Quartslab and they have the list for this radio so all is in order....many thanks for your replies,...