Re: LF: Re: MF/160

[Andy Talbot <andy.g4jnt@gmail.com>]

I bought it before Ebay was even a glimmer in someone's eye.  Made by Eltek,  there doesn't seem to be a tyoe number.  Its an old 48cm rack-mounted sized ex telephone exchange job. 

I dived inside and added a voltage adjust facility on the front panel so it could be varied between 24 - 60V, put some high current screw terminals in place of the blade connector and added a DVM module in place of the analogue panel V-meter

Andy 'jnt

On 24 October 2017 at 13:59, <i.frith@ntlworld.com> wrote:

Hi Andy

 

I, like you use SMPSU’s 50V approx 10A . Mine are Chinese albeit shipped in the UK! was a bit dirty but all it needed was a mains input filter. Now very quiet. Wonder what type/model/EBay number you are using. I went for a pair of 28V 10A units so I could use 56 or 28 V on the 472 KHz TX.

 

Thanks

73 Ian G4GIR

 

 

Whic

 

From: Andy Talbot

Sent: Monday, October 23, 2017 8:20 PM

To: rsgb_lf_group@blacksheep.org

Subject: Re: Re: Re: LF: MF/160

 

I don't knoe why radio amateurs are so anti SMPSU on principle.   

Unfiltered nasty Chinese ones may be bad, but anything can be cleaned up. 

 

My 50 Volt 20A one I use with teh 475kHz PA is absolutely quiet, not a whisper detectable on any frequency from LF to HF

 

'jnt

 

 

On 23 October 2017 at 20:07, dhchurch <dhchurch@lineone.net> wrote:

Hello Andy

 

The idea of using any SMPS in, or near, the shack is somewhat abhorrent. It is possible to introduce a series circuit in a linear PSU which is not exactly a regulator but has a hum cancellation circuit, something that used to appear in an ancient National Semiconductor publication. I'd love to try it but just haven't left any room in my PSUs, they're stuffed full, including a cooling fan. A couple of 100Hz side bands are at least predictable, my PA has,  but there is one regular transmission on LF which has all manner of spurii making reception here somewhat variable.

 

I think Dave, GW8GLO, has a system which promptly knocks off his transmitter SMPS when going into Rx mode, maybe this is the way to go.

 

73, Hugh, M0DSZ

 

----- Receiving the following content -----

From: Andy Talbot

Receiver: rsgb_lf_group

Time: 2017-10-23, 10:12:17

Subject: Re: Re: LF: MF/160

 

Its a difficult call - I have a similar problem with my 700 Watt 137kHz Tx.　 　30dB hum sidebands corresponds to 3% ripple, which in the main scheme of things is not that much.　 　It would need an enormous reservoir capacitor to make a serious reduction.　　

 

Either that or design the Tx to run from 50V and use a SMPSU instead of raw rectified AC

 

Andy　 G4JNT

 

On 23 October 2017 at 10:03, dhchurch <dhchurch@lineone.net> wrote:

Mal, I think a little attention should be paid to, perhaps, your power supply.　The 100Hz sidebands, as I recall from earlier this week, should be much lower in level. Seen on Spectrum Lab　at one stage, they were less than -30dB in comparative level.　

　

73, Hugh, M0DSZ

　

----- Receiving the following content -----

From: Andy Talbot

Receiver: rsgb_lf_group

Time: 2017-10-22, 22:44:59

Subject: Re: LF: MF/160

 

You're so strong, Mal,　 I'm getting decodes on your hum sidebands

 

21:36　　G3KEV　　0.475804　　-27　　0　　IO94sh　　5　　G4JNT　　IO90iv　　384　　189　　2017-10-22 21:36　　G3KEV　　0.475704　　+3　　0　　IO94sh　　5　　G4JNT　　IO90iv　　384　　189　　2017-10-22 21:36　　G3KEV　　0.475604　　-29　　0　　IO94sh　　5　　G4JNT　　IO90iv　　384　　189　　2017-10-22 1

 

Andy　 　G4JNT

 

On 22 October 2017 at 19:25, mal hamilton <g3kevmal@talktalk.net> wrote:

NICE CONDX 160M THIS EVENING VK7DIK 　REPORTING G3KEV WSPR MODE

LOOKING GOOD FOR MF/630 M ALSO

TNX REPORT DE MAL/G3KEV

　

　

　

　

　

　

　

　

　

　

　

　

　

　

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