LF: Re: Decca Experts - Converting Red to Purple ?

["mal hamilton" <g3kevmal@talktalk.net>]

GUARD CCT

LOW BAND IS C1 –330nF plus C2 –470nF in parallel resonates with the link winding of 9 turns

The link winding has 9 turns on LOW band units and should be within tolerance for73 khz

6F units/85 Khz had 59 turns on main coil,  5F units would have more turns.

Hope this helps

de mal/g3kev

 

 

 

From: Warren Ziegler

Sent: Monday, August 05, 2013 2:27 PM

To: rsgb_lf_group

Subject: Re: LF: Re: Decca Experts - Converting Red to Purple ?

 

Mal,

    Many thanks for the info on the low bad Decca tanks!

Does your handbook call out the specs for the guard circuit (link coil and capacitance)?

 

73 Warren

 

On Mon, Aug 5, 2013 at 8:00 AM, mal hamilton <g3kevmal@talktalk.net> wrote:

Hi Warren

Decca LOW BAND --------------inductor L reqd to resonate on 73 khz ------------126.75 uH ie  Total C in PA unit 37.5 nF plus 126.75 uH in series ===== 73 Khz

High band versions do not have enough C in PA UNIT

73 DE MAL/G3KEV

 

 

 

From: Warren Ziegler

Sent: Monday, August 05, 2013 1:59 AM

To: rsgb_lf_group

Subject: Re: LF: Fw: Decca Experts - Converting Red to Purple ?

 

Hi Mal,

 

   Many thanks for the e-mail!

I am looking for details on the tank circuit for the "Purple" Decca which was on 70.8 kHz - either inductance or number of turns or capacitance. Also, any details on the guard circuit for the 70kHz version - how many turns on the link and capacitance.

I have an unconverted 112kHz unit, not sure if that is considered high band or low band?

 

    I really appreciate your help!

 

vy 73 Warren K2ORS

 

On Sun, Aug 4, 2013 at 3:08 PM, mal hamilton <g3kevmal@talktalk.net> wrote:

 

 

From: mal hamilton

Sent: Sunday, August 04, 2013 7:59 PM

To: rsgb_lf_group@blacksheep.org

Subject: Re: LF: Decca Experts - Converting Red to Purple ?

 

Warren

I have all the original handbooks for the Decca 5501 range if you need specific info let me know. The low band versions have a different Capacitor board and are easy to mod for 73 Khz

The higher band versions are not so convenient to mod for 73 but more suited to 136.

I have 2 x 5501 units for the high band modified for 136 but fortunately I have 2 x C boards  for the low band so I just need to modify the Coils for 73 if we got this band again

I was active on 73 towards the end but by then nearly everyone had moved to 136

Most hams in the UK were using modified Audio amps on 73 and I do not recall anyone using the decca on that band at the time. Decca amps were not available in the early days of 73

Modes at the time were CW and QRSS

mal/g3kev

 

 

 

 

 

 

 

 

From: Warren Ziegler

Sent: Sunday, August 04, 2013 1:28 AM

To: rsgb_lf_group

Subject: LF: Decca Experts - Converting Red to Purple ?

 

Hello to all of the Decca Navigator experts out there...

 

    I have an unconverted Decca 5501 transmitter which is marked "Red" - I believe that is 112kHz - would like to run it on 73kHz.  The tank coil reads about 80uH, can I just pad it down with more "C" to get to 73kHz or would that mess up the L/C ratio and thus lower the loaded "Q" ?

 

    Another question - anyone have a spare "Purple" Decca on 71kHz that they would consider parting with?

 

 

 

--
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1

                WG2XRS/1

 

 

--
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1

 

 

--
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1