The British Caving Association

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Author:  dlbritton [ Fri 09 Aug 2013 17:19 ]
Post subject:  Heyphone

Not worried about compatibility.
Which Heyphone should I build. 87Khz or 38 Khz?

Danny Britton

Author:  Rob Gill [ Sat 10 Aug 2013 12:56 ]
Post subject:  Re: Heyphone

87kHz is likely to be affected by LORAN transimssions centred on 100kHz to a greater or lesser extent depending on location. I only played with John Hey's 38kHz version briefly but I seem to recall that performance in other respects was as good as the 87kHz version.

So, assuming that you are using the standard earth current electrodes rather than any form of resonant loop antenna, I'd go for 38kHz. (I can't think of any particular reason to use loops, but you might find it difficult to come up with an efficient loop design of sufficient bandwidth at that lower frequency.)

Look forward to hearing of your experiences at 38kHz!


Author:  John Rabson [ Mon 16 Sep 2013 17:27 ]
Post subject:  Re: Heyphone (parts list)

This is a reply to an enquiry received some weeks ago. Unfortunately, the emails concerned got stratified for which I apologise. If anybody finds any errors or omissions, please would they let me know.

The components list for the Heyphone (with a few updates) is at

Most components can be got from a range of suppliers, but one or two things seem to be a bit special. At the end of the list there is some
contact information. This relates to UK suppliers, but I have found possible alternatives in the US.

Farnell (a.k.a. FEC) has an outlet in the US at

RS Components (known once upon a time as RadioSpares) appears to be affiliated with

Maplin Electronics ( do not seem to have any outlets in the US, but if you consult their website and search for component catalogue numbers, you should be able to establish the characteristics of what you need to look for from a US supplier.

I believe the Toko 360 µH inductors are no longer made, but John Hey uses small fixed inductors of 330 micro henries (they look like 1/4 W resistors
and are made by many companies). He adjusts the value of the parallel capacitor (originally 10 nF) so as to achieve resonance.

Author:  jtml [ Wed 17 Dec 2014 02:36 ]
Post subject:  Re: Heyphone

I have an immediate (well, within several months) use for a simple through-earth voice comm set, through 100 feet of limestone. Would prefer not loop but wire/stakes for transmission and reception, so Hey phone comes to mind. Does anyone have a pair of them (beaters are fine) that they would like to part with? I think the Nicola III is a bit overkill for this app, and my design is a box of parts and hand drawn schematic but no board made as of yet. SSB and 30-40 KHz should suffice. Thanks, if anyone still reads this.
John Lyles
New Mexico, USA

Author:  Adam Pyka [ Mon 02 Feb 2015 16:53 ]
Post subject:  Re: Heyphone (parts list)

Hello all!
John Rabson wrote:
I believe the Toko 360 µH inductors are no longer made, but John Hey uses small fixed inductors of 330 micro henries (they look like 1/4 W resistors
and are made by many companies). He adjusts the value of the parallel capacitor (originally 10 nF) so as to achieve resonance.

I'm trying to replace the TOKO inductor for the fork of oryginal Heyphone described here, but I cannot found any inductor which has similar parameters. Anybody has an idea what can I place instead of RWO6A6408?

All the best!

Author:  Rob Gill [ Tue 03 Feb 2015 09:18 ]
Post subject:  Re: Heyphone


The type of inductor suggested as a replacement by John Hey is generally described as an 'axial inductor'. A Google search for 'axial inductor 330uH' will provide a number of links such as: ... /dp/608579 and numerous eBay links (which may be more convenient for small orders).

As noted, it will be necessary to optimise the associated capacitor to obtain resonance.

I have no experience of using this type of inductor as a substitute for the original Toko coil, so would be very pleased to hear how well it works.

Best regards

Author:  AMW [ Tue 03 Feb 2015 21:31 ]
Post subject:  Re: Heyphone

CPC is Farnells hobbyist outlet.


Author:  Daniel Chailloux [ Thu 12 Feb 2015 08:43 ]
Post subject:  Re: Heyphone


I am looking for 5.568 MHz quartz crystals used as local oscillator in the Heaphone project but I cannot found any crystal at this frequency.
Anybody has an idea ?

Greetings from France,

Author:  Daniel Chailloux [ Sat 14 Feb 2015 16:12 ]
Post subject:  Re: Heyphone

HeyPhone project :

After several email exchanges with John Hey and data collected on GREGJ, I would like to resume and give you some technical answers concerning the HeyPhone project.

1 - Toko coils : the original variable coils, L1, L2 and L3, can be replaced by fixed coils like Inductor axial 330µH - EPCOS B78108S1334J INDUCTOR, AXIAL, 330UH, ref Farnell : 608579. You will have to adjust the capacitors C1, C6 (RX) and C35 (TX) around 10 nF.

2 - Antenna transformer : The original core and former can be replace respectively by EPCOS B66325GX127 (Core - Farnell ref : 1190595) and EPCOS B66242J1000R1 (Former - Farnell ref : 1190598).
Copper wires (AWG23 and AWG18) can be found on eBay. Key-words : Enamelled Copper Winding Wire.

3 - 5.568 MHz crystal : From John Hey, this is a custom value to be compatible with the MolePhone.
QuartSLab, which manufactured these HeyPhone quartz, has still the specification details and is therefore able to manufacture these crystals. They can supply two 5.56800MHz, HC49u Crystals at a total cost of £32.96 GBP, i.e. £16.48 each inc. shipping.
QuartSLab Website :

Hoping this helps,

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