EMRFD pages 8.8 through 8.11. "Tunable or common mode hum". Thing is this is usually only a big problem on direct conversion receivers and the SW40+ is a superhet. Still, having built some superhets with lots of RF leakage through the mixers, I can assure you that if you have enough leakage of the BFO out and back in that you can have comm
| 5492
| 2010-11-30 00:42:28
| Tamás Fábián
| Re: Strange, annoying power supply problem
|
I checked my setup and I found a ground loop: the counterpoise AND the power supply was grounded separately. After eliminating the ground loop (by changing the antenna setup), the hum did not decrease. I even more convinced that the RF coming from the antenna somehow affects the rectifier in the supply. Next time I'll try to add RF bypass capacitors parallel to the diodes in the rectifier and see if it helps. Thank you for your advice! On 29 November 2010 20:30, PD <pawlud@gmail.com> wrote:
> Probably you have an ground loop problem, common with mains power supply.
> Check your ground system you are feeding to the rig.
> Try to use a single ground system. Ground to to central point, avoid many
> wires carrying the ground.
>
>
>
> On 29 November 2010 20:20, Tamás Fábián <giganetom@gmail.com> wrote:
>
>>
>>
>> Hello,
>>
>> I've just completed Dave Benson's SW40+ transciever. It works FB when
>> I feed it form batteries.
>>
>> But when I use simple 230V AC / 12V DC supplies I hear intense hum
>> along with the sidetone. The hum is only apparent when I connect the
>> rig to the antenna. If I use a dummy load, no or very little hum is
>> present. Antenna is a random wire on the balcony, tuned with an
>> L-match, SWR is < 1.2 from 7000-7035 (all across the tuning range).
>>
>> With a dummy load the hum completely disappears at 1-1.5 Watts, with
>> an antenna the hum is audible even when is almost no power coming out
>> of the radio.
>>
>> I have two theories:
>>
>> 1. The RF power gets into the power supply and somehow messes with the
>> diodes
>>
>> 2. The power line acts as a counterpoise. The diodes are
>> "disconnecting" the "counterpoise" 100 times in a second...
>>
>> Which - if any - of these theories are correct (if the first one is,
>> what is happening exatly) and what is more importatnt: how do I get
>> rid of the hum?
>>
>> Thanks in advance,
>>
>> Tamas FABIAN, HA5FTL
>>
>>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
> |
| 5495
| 2010-11-30 07:43:48
| PD
| Re: Strange, annoying power supply problem
|
Tomas, In my opinion, the best way to eliminate any RF from interfering with the PSU, is to filter by means of ferrite rings and caps to ground. I have lots of them salvaged from old TV sets. They are very effective. At present, I am doing a project, which involves feeding the dc power to some six different, interconnected modules together. In order to eliminate hum, I just feed only the +ve supply lead to each module, and put one SINGLE - ve lead to just one single module in the middle. Thus, the -ve travels throu the coax shield of the interconnecting cables of each module. Paul 9H1FQ On 30 November 2010 09:42, Tam�s F�bi�n <giganetom@gmail.com> wrote:
>
>
> I checked my setup and I found a ground loop: the counterpoise AND the
> power supply was grounded separately.
>
> After eliminating the ground loop (by changing the antenna setup), the
> hum did not decrease.
>
> I even more convinced that the RF coming from the antenna somehow
> affects the rectifier in the supply. Next time I'll try to add RF
> bypass capacitors parallel to the diodes in the rectifier and see if
> it helps.
>
> Thank you for your advice!
>
> On 29 November 2010 20:30, PD <pawlud@gmail.com >
> wrote:
> > Probably you have an ground loop problem, common with mains power
> supply.
> > Check your ground system you are feeding to the rig.
> > Try to use a single ground system. Ground to to central point, avoid many
> > wires carrying the ground.
> >
> >
> >
> > On 29 November 2010 20:20, Tam�s F�bi�n <giganetom@gmail.com>
> wrote:
> >
> >>
> >>
> >> Hello,
> >>
> >> I've just completed Dave Benson's SW40+ transciever. It works FB when
> >> I feed it form batteries.
> >>
> >> But when I use simple 230V AC / 12V DC supplies I hear intense hum
> >> along with the sidetone. The hum is only apparent when I connect the
> >> rig to the antenna. If I use a dummy load, no or very little hum is
> >> present. Antenna is a random wire on the balcony, tuned with an
> >> L-match, SWR is < 1.2 from 7000-7035 (all across the tuning range).
> >>
> >> With a dummy load the hum completely disappears at 1-1.5 Watts, with
> >> an antenna the hum is audible even when is almost no power coming out
> >> of the radio.
> >>
> >> I have two theories:
> >>
> >> 1. The RF power gets into the power supply and somehow messes with the
> >> diodes
> >>
> >> 2. The power line acts as a counterpoise. The diodes are
> >> "disconnecting" the "counterpoise" 100 times in a second...
> >>
> >> Which - if any - of these theories are correct (if the first one is,
> >> what is happening exatly) and what is more importatnt: how do I get
> >> rid of the hum?
> >>
> >> Thanks in advance,
> >>
> >> Tamas FABIAN, HA5FTL
> >>
> >>
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>
>
[Non-text portions of this message have been removed] |
| 5499
| 2010-12-01 01:29:57
| Tamás Fábián
| Re: Strange, annoying power supply problem
|
Hello, Thank you for your advise, I'll to filter the RF currents going into the PSU. Should I use a common or differential mode choke (or both?) Two fellow HAMs suggested that I should solder 10-100nF capacitors parallel to each rectifier diode. I did the work and it helped a LOT. Almos no hum. Almost. Hope extra filtering will help. On 30 November 2010 16:42, PD <pawlud@gmail.com> wrote:
> Tomas,
>
> In my opinion, the best way to eliminate any RF from interfering with the
> PSU, is to filter by means of ferrite rings and caps to ground. I have lots
> of them salvaged from old TV sets. They are very effective.
>
> At present, I am doing a project, which involves feeding the dc power to
> some six different, interconnected modules together. In order to eliminate
> hum, I just feed only the +ve supply lead to each module, and put one
> SINGLE - ve lead to just one single module in the middle. Thus, the -ve
> travels throu the coax shield of the interconnecting cables of each module.
>
> Paul
> 9H1FQ
>
> On 30 November 2010 09:42, Tamás Fábián <giganetom@gmail.com> wrote:
>
>>
>>
>> I checked my setup and I found a ground loop: the counterpoise AND the
>> power supply was grounded separately.
>>
>> After eliminating the ground loop (by changing the antenna setup), the
>> hum did not decrease.
>>
>> I even more convinced that the RF coming from the antenna somehow
>> affects the rectifier in the supply. Next time I'll try to add RF
>> bypass capacitors parallel to the diodes in the rectifier and see if
>> it helps.
>>
>> Thank you for your advice!
>>
>> On 29 November 2010 20:30, PD <pawlud@gmail.com >
>> wrote:
>> > Probably you have an ground loop problem, common with mains power
>> supply.
>> > Check your ground system you are feeding to the rig.
>> > Try to use a single ground system. Ground to to central point, avoid many
>> > wires carrying the ground.
>> >
>> >
>> >
>> > On 29 November 2010 20:20, Tamás Fábián <giganetom@gmail.com>
>> wrote:
>> >
>> >>
>> >>
>> >> Hello,
>> >>
>> >> I've just completed Dave Benson's SW40+ transciever. It works FB when
>> >> I feed it form batteries.
>> >>
>> >> But when I use simple 230V AC / 12V DC supplies I hear intense hum
>> >> along with the sidetone. The hum is only apparent when I connect the
>> >> rig to the antenna. If I use a dummy load, no or very little hum is
>> >> present. Antenna is a random wire on the balcony, tuned with an
>> >> L-match, SWR is < 1.2 from 7000-7035 (all across the tuning range).
>> >>
>> >> With a dummy load the hum completely disappears at 1-1.5 Watts, with
>> >> an antenna the hum is audible even when is almost no power coming out
>> >> of the radio.
>> >>
>> >> I have two theories:
>> >>
>> >> 1. The RF power gets into the power supply and somehow messes with the
>> >> diodes
>> >>
>> >> 2. The power line acts as a counterpoise. The diodes are
>> >> "disconnecting" the "counterpoise" 100 times in a second...
>> >>
>> >> Which - if any - of these theories are correct (if the first one is,
>> >> what is happening exatly) and what is more importatnt: how do I get
>> >> rid of the hum?
>> >>
>> >> Thanks in advance,
>> >>
>> >> Tamas FABIAN, HA5FTL
>> >>
>> >>
>> >
>> >
>> > [Non-text portions of this message have been removed]
>> >
>> >
>> >
>> > ------------------------------------
>> >
>> > Yahoo! Groups Links
>> >
>> >
>> >
>> >
>>
>>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
> |
| 5500
| 2010-12-01 02:01:44
| PD
| Re: Strange, annoying power supply problem
|
Common or differential is a matter of experiment, as there are many factors to consider. I have tried differential, with two coils in opposite phase to phasing out the offending currents and are very effective ! On 1 December 2010 10:29, Tam�s F�bi�n <giganetom@gmail.com> wrote:
>
>
> Hello,
>
> Thank you for your advise, I'll to filter the RF currents going into the
> PSU.
>
> Should I use a common or differential mode choke (or both?)
>
> Two fellow HAMs suggested that I should solder 10-100nF capacitors
> parallel to each rectifier diode. I did the work and it helped a LOT.
> Almos no hum. Almost. Hope extra filtering will help.
>
>
> On 30 November 2010 16:42, PD <pawlud@gmail.com >
> wrote:
> > Tomas,
> >
> > In my opinion, the best way to eliminate any RF from interfering with the
> > PSU, is to filter by means of ferrite rings and caps to ground. I have
> lots
> > of them salvaged from old TV sets. They are very effective.
> >
> > At present, I am doing a project, which involves feeding the dc power to
> > some six different, interconnected modules together. In order to
> eliminate
> > hum, I just feed only the +ve supply lead to each module, and put one
> > SINGLE - ve lead to just one single module in the middle. Thus, the -ve
> > travels throu the coax shield of the interconnecting cables of each
> module.
> >
> > Paul
> > 9H1FQ
> >
> > On 30 November 2010 09:42, Tam�s F�bi�n <giganetom@gmail.com>
> wrote:
> >
> >>
> >>
> >> I checked my setup and I found a ground loop: the counterpoise AND the
> >> power supply was grounded separately.
> >>
> >> After eliminating the ground loop (by changing the antenna setup), the
> >> hum did not decrease.
> >>
> >> I even more convinced that the RF coming from the antenna somehow
> >> affects the rectifier in the supply. Next time I'll try to add RF
> >> bypass capacitors parallel to the diodes in the rectifier and see if
> >> it helps.
> >>
> >> Thank you for your advice!
> >>
> >> On 29 November 2010 20:30, PD <pawlud@gmail.com > 40gmail.com>>
>
> >> wrote:
> >> > Probably you have an ground loop problem, common with mains power
> >> supply.
> >> > Check your ground system you are feeding to the rig.
> >> > Try to use a single ground system. Ground to to central point, avoid
> many
> >> > wires carrying the ground.
> >> >
> >> >
> >> >
> >> > On 29 November 2010 20:20, Tam�s F�bi�n <giganetom@gmail.com
> >
>
> >> wrote:
> >> >
> >> >>
> >> >>
> >> >> Hello,
> >> >>
> >> >> I've just completed Dave Benson's SW40+ transciever. It works FB when
> >> >> I feed it form batteries.
> >> >>
> >> >> But when I use simple 230V AC / 12V DC supplies I hear intense hum
> >> >> along with the sidetone. The hum is only apparent when I connect the
> >> >> rig to the antenna. If I use a dummy load, no or very little hum is
> >> >> present. Antenna is a random wire on the balcony, tuned with an
> >> >> L-match, SWR is < 1.2 from 7000-7035 (all across the tuning range).
> >> >>
> >> >> With a dummy load the hum completely disappears at 1-1.5 Watts, with
> >> >> an antenna the hum is audible even when is almost no power coming out
> >> >> of the radio.
> >> >>
> >> >> I have two theories:
> >> >>
> >> >> 1. The RF power gets into the power supply and somehow messes with
> the
> >> >> diodes
> >> >>
> >> >> 2. The power line acts as a counterpoise. The diodes are
> >> >> "disconnecting" the "counterpoise" 100 times in a second...
> >> >>
> >> >> Which - if any - of these theories are correct (if the first one is,
> >> >> what is happening exatly) and what is more importatnt: how do I get
> >> >> rid of the hum?
> >> >>
> >> >> Thanks in advance,
> >> >>
> >> >> Tamas FABIAN, HA5FTL
> >> >>
> >> >>
> >> >
> >> >
> >> > [Non-text portions of this message have been removed]
> >> >
> >> >
> >> >
> >> > ------------------------------------
> >> >
> >> > Yahoo! Groups Links
> >> >
> >> >
> >> >
> >> >
> >>
> >>
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>
>
>
[Non-text portions of this message have been removed] |
| 5504
| 2010-12-03 21:39:13
| longjohn119
| Re: Strange, annoying power supply problem
|
Do you have a balun at the fed point of the antenna to decouple it from the transmission line (coax)? Without a proper balun (Technically an unun in this case) random wires are big noise magnets because of the common mode currents on the feedline. It probably wouldn't hurt your ERP any either
| 5505
| 2010-12-05 22:51:43
| Tamás Fábián
| Re: Strange, annoying power supply problem
|
Hello, I use an air-core autotransformer unun to match the short random wire to the coax. I tried two things this far and both helped a lot, together they eliminated the problem. I very rarely hear a faint hum in the sidetone. Still not always perfect, but much-much better. Here is what I have done: - I put 10nF ceramic capacitors parallel to the rectifier diodes (Graetz bridge). This reduced the hum greatly. I did not try greater capacitors or shunting the voltage regulator, these might worth a try. - A common mode ferrite choke was put onto the 12V supply cable coming from the supply, closest to it. The ferrite core is similar to this one: http://www.fast-lad.co.uk/store/rl-choke_snap-on_ferrite_choke_%28choke-ferrite%29-p-4964.html I wound three turns onto it, and the hum was gone. I did not try to remove the capacitors after the choke was put on, so I don't know which helps more. Maybe I will experiment with it a little bit more. It would be interesting to create a device that is able to measure the common mode _and_ differential mode rf currents in a pair of wires. It could be used to track these kind of problems and also to detect spurious coax braid current (or common mode current on ladder lines). What do you think? On 4 December 2010 06:39, longjohn119 < some_oil_with_your_teaparty@yahoo.com > wrote:
>
>
> Do you have a balun at the fed point of the antenna to decouple it from the
> transmission line (coax)? Without a proper balun (Technically an unun in
> this case) random wires are big noise magnets because of the common mode
> currents
| 5517
| 2010-12-09 06:29:35
| longjohn119
| Re: Strange, annoying power supply problem
|
I'd leave the caps across the rectifier diodes. I do that in every power supply I build after seeing it's effects in tube guitar amplifiers with solid state rectifiers, especially the souped up hi-gain ones over 25 years ago. I noticed that all the hi-end road and studio gear had them in the power supplies. I habitually add them to my stuff when I clean or service it, it's just dirt cheap insurance especially when you buy the caps in bulk. It's like the reverse diode across the input and output of a 3 terminal linear regulator. To me it's just part of the basic circuit but I see it left out in so many, even professional, designs. It's especially important in audio and other circuits where you use large electrolytics on the power lines for filtering. Last thing you want is those juiced up electrolytics all discharging through the regulator in reverse when you shut the power off .... Sometimes you need more than one ferrite to get the job done. I have 3 on each end of my serial cable going to my RX320D because that's what it took to knock down that noise in the already noisy LF band. Above LF though it wasn't a problem but I'm sure the RX320D is like most commercial receivers, LF is almost an afterthought (Made obvious because it has 20 db or more attenuation below 500Khz unaltered) so the circuit power filtering, especially in the digital portion, isn't exactly optimized for it. JR
| 5518
| 2010-12-09 07:03:37
| Tamás Fábián
| Re: Strange, annoying power supply problem
|
John ang Group, I was in the wrong track. Despite the fact all modifications are helped to reduce the hum, these wasn't THE solution for the problem. I recently bought a large (well, for qrp ;) ) lead-acid battery for long /P actions, and when I connected to the rig, the hum came back 10 times stronger (!!!) than before. Than I tried to snap filter ferrites on every cable going on or out of the rig. When I put a ferrite on the headphone cable, the hum disappeared. I plugged the ac/dc supply back on and the hum did not come back. I removed every filter ferrite but the one on the headphone and still no hum at all. I guess it's the same as the tunable hum at dc receivers, there is only two difference: - It's not tunable, since SW40 is a superhet receiver - It only audible at transmit, because the sidetone is working by "receiving" the rig's own signal. This is when all the RF leakage / mix with 50Hz stuff occures. Thank you all for your precious help, every advice helped a bit to solve this rather frustrating issue. Good bye and Happy Holidays to everyone! On 9 December 2010 15:29, longjohn119 < some_oil_with_your_teaparty@yahoo.com > wrote:
>
>
> I'd leave the caps across the rectifier diodes. I do that in every power
> supply I build after seeing it's effects in tube guitar amplifiers with
> solid state rectifiers, especially the souped up hi-gain ones over 25 years
> ago. I noticed that all the hi-end road and studio gear had them in the
> power supplies. I habitually add them to my stuff when I clean or service
> it, it's just dirt cheap insurance especially when you buy the caps in bulk.
>
>
> It's like the reverse diode across the input and output of a 3 terminal
> linear regulator. To me it's just part of the basic circuit but I see it
> left out in so many, even professional, designs. It's especially important
> in audio and other circuits where you use large electrolytics on the power
> lines for filtering. Last thing you want is those juiced up electrolytics
> all discharging through the regulator in reverse when you shut the power off
> ....
>
> Sometimes you need more than one ferrite to get the job done. I have 3 on
> each end of my serial cable going to my RX320D because that's what it took
> to knock down that noise in the already noisy LF band. Above LF though it
> wasn't a problem but I'm sure the RX320D is like most commercial receivers,
> LF is almost an afterthought (Made obvious because it has 20 db or more
> attenuation below 500Khz unaltered) so the circuit power filtering,
> especially in the digital portion, isn't exactly optimized for it.
>
> JR
>
>
| 5522
| 2010-12-11 03:31:36
| longjohn119
| Re: Strange, annoying power supply problem
|
Thanks for reporting back with the solution. Especially important
| 5918
| 2011-03-14 11:40:47
| Tamás Fábián
| Re: Strange, annoying power supply problem
|
Late-late-late feedback on this: I've built a K1EL keyer. It worked nicely alone, but it went haywire with the radio. I could not resolve the problem quickly so I threw it into the drawer for later investigation. I'm building a new antenna tuner and went into the topic quite a lot deeper than ever before and I discovered that how feedline current balance should be kept good. I've used one the snap-on ferrite chokes to improvise a Guanella balun on the RG58 feedline just before my old tuner (can be seen at http://qrz.com/db/HA5FTL). The buzzing has gone. The K1EL keyer suddenly worked correctly. It was improper feedline balance the whole time. The ferrites in the old configuration mitigated the problem by providing high impedance for the rf current towards my head and hands (picture at qrz.com, rig with the gray chokes). But this is clearly not a good nor a stable solution. The correct(er HI) solution is to provide common mode feedline current with high impedance before the tuner. vy 73 es gd dx de ha5ftl. On 11 December 2010 12:31, longjohn119 < some_oil_with_your_teaparty@yahoo.com> wrote: >
>
> Thanks for reporting back with the solution. Especially important
| | | | | | |