| |
CX2SA > SATDIG 02.01.09 23:45l 415 Lines 12789 Bytes #999 (0) @ WW
BID : 63748_CX2SA
Read: GUEST
Subj: AMSAT-BB-digest V4 6
Path: IZ3LSV<IK2XDE<DB0RES<DK0WUE<7M3TJZ<HG8LXL<CX2SA
Sent: 090102/2233Z @:CX2SA.LAV.URY.SA #:63748 [Minas] FBB7.00e $:63748_CX2SA
From: CX2SA@CX2SA.LAV.URY.SA
To : SATDIG@WW
Today's Topics:
1. Re: G-5500 stuck problem (Art McBride)
2. Re: Question adding RHCP to Cheap Yagi (Curt Nixon)
3. Re: Question adding RHCP to Cheap Yagi (Greg D.)
4. Re: Ham-Mag (Clint Bradford)
----------------------------------------------------------------------
Message: 1
Date: Fri, 2 Jan 2009 10:01:09 -0800
From: "Art McBride" <kc6uqh@xxx.xxx>
Subject: [amsat-bb] Re: G-5500 stuck problem
To: "'Greg D.'" <ko6th_greg@xxxxxxx.xxx>, <wa6fwf@xxxxxxxxx.xxx>,
<amsat-bb@xxxxx.xxx>
Message-ID: <4320416054294C8A9CFDF44DD898E2CB@xxxxxx>
Content-Type: text/plain; charset="us-ascii"
To All,
Antenna rotator motors are capacitor run types. All induction motors shift
the phase of the current. The current is nearest to being in phase only when
the rotor is locked. An unloaded motor draws almost no power as the current
is out of phase with the voltage. As the antenna rotators age, the run
capacitor looses capacity causing a reduction in torque from the motor. This
capacitor is in the control box, is low cost and the first thing that should
be replaces if the rotator is slowing down. Typically the run capacitor only
lasts for 10 years of service. TV antenna rotators did not last that long
but the Amateur Radio antenna rotators will often outlast the run capacitor.
Art, KC6UQH
-----Original Message-----
From: amsat-bb-bounces@xxxxx.xxx [mailto:amsat-bb-bounces@xxxxx.xxxx On
Behalf Of Greg D.
Sent: Thursday, January 01, 2009 11:09 PM
To: wa6fwf@xxxxxxxxx.xxxx amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: G-5500 stuck problem
Hi Kevin,
So, my take-away here is that it's not the stall itself that is the problem;
the motor is practically designed to self-destruct. Simply running the
rotor back and forth enough times will do the same thing. In fact, probably
worse, given the higher draw.
One thing just occurred to me... AC current measurements assume a specific
phase relationship between voltage and current - power factor, I think they
call it. This is a highly inductive load, and the phase-shift capacitor
throws another unknown into the puzzle. I wonder if the two measurements
you took are real? It could be that you think that the running current is
higher, when it may just be a measurement error. How were they measured?
Greg KO6TH
> From: wa6fwf@xxxxxxxxx.xxx
> To: amsat-bb@xxxxx.xxx
> Date: Thu, 1 Jan 2009 20:51:47 -0800
> Subject: [amsat-bb] Re: G-5500 stuck problem
>
> Hi Greg,
> these transformers and motors are rated for intermittent duty so getting
them stuck and left that way kills them, if memory serves
> they pull about 1.7 amps running, and drop to about 1.2 amps stalled,
1.2amps x 25v = 30 watts and over time that heat builds up and
> fries the windings.
>
> It's just a oddity of this particular type of ac motor that it behaves
this way, if it was another type or a dc motor you would see
> the current rise that you expected and fuses would pop.
>
> I found this out when I was making a add on card to my LVB tracker to
replace the G-5500 control box, I thought I would be slick
> and add one of the PPTC resettable fuses on the motors, so I needed to
know the running current and locked current so I could pick
> the right one, I was also surprised when the current dropped a little
instead of going up, and then doing some reading on the web
> about dual winding AC motors that use a capacitor to phase shift the
other winding explained why this happens.
>
> 73
> Kevin WA6FWF
>
>
> ----- Original Message -----
> From: "Greg D." <ko6th_greg@xxxxxxx.xxx>
> To: <wa6fwf@xxxxxxxxx.xxx>; <amsat-bb@xxxxx.xxx>
> Sent: Thursday, January 01, 2009 7:04 PM
> Subject: RE: [amsat-bb] Re: G-5500 stuck problem
>
>
>
> Ha, really... Thanks, I was "sure" it was the other way around.
>
> So, if the current drops a little on a jam, why would it burn up either
the transformer or motor?
>
> Greg KO6TH
>
>
> > From: wa6fwf@xxxxxxxxx.xxx
> > To: amsat-bb@xxxxx.xxx
> > Date: Thu, 1 Jan 2009 18:42:15 -0800
> > Subject: [amsat-bb] Re: G-5500 stuck problem
> >
> > Hi Greg,
> > Actually you need to measure the current while it is moving, then if
it drops a little then its a jam, if it goes to zero then
> > its the limit switch.
> >
> > I know this goes against reasoning, you expect a locked motor to pull
more current, but these are split winding AC motors with a
> > capacitor and they act differently.
> >
> > This is also why when you get a cable snag you burn up the motor or the
transformer or both before you blow the fuse, that fuse I
> > think just saves you from a mis-wired or shorted cable.
> >
> > 73
> > Kevin WA6FWF
> >
> .
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
_________________________________________________________________
Life on your PC is safer, easier, and more enjoyable with Windows VistaR.
http://clk.atdmt.com/MRT/go/127032870/direct/01/
_______________________________________________
Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
__________ Information from ESET NOD32 Antivirus, version of virus signature
database 3731 (20090101) __________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com
__________ Information from ESET NOD32 Antivirus, version of virus signature
database 3731 (20090101) __________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com
__________ Information from ESET NOD32 Antivirus, version of virus signature
database 3732 (20090102) __________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com
__________ Information from ESET NOD32 Antivirus, version of virus signature
database 3732 (20090102) __________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com
------------------------------
Message: 2
Date: Fri, 02 Jan 2009 13:02:36 -0500
From: Curt Nixon <cptcurt@xxxxx.xxx>
Subject: [amsat-bb] Re: Question adding RHCP to Cheap Yagi
To: Howard Long <howard@xxxxxxxxxx.xxx>
Cc: 'AMSAT-BB' <amsat-bb@xxxxx.xxx>
Message-ID: <495E56BC.4060302@xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Thanks Howard...Thin I've got it. Its going up this afternoon. Boom is
drilled, elements made. Just mounting them now and then the harness..
Curt
Howard Long wrote:
> Hi Curt
>
> There are several ways to skin the same cat.
>
> Although they are fed in phase, they are orthogonally mounted and with their
> spatial separation a 90 degree phase delay is created, thus creating CP.
>
> If the elements are still orthogonal but are at the same location along the
> boom, then the delay would need to be inserted electrically, with an
> electrical 1/4 wave section of 50 ohm coax. Some CP antennas use a
> combination of both spatial and electrical phase difference.
>
> To switch RHCP to LHCP can be achived by any of the following three means:
>
> O Insert an additional 180 degree electrical delay between one arm of the
> power splitter and the antenna, with an electrical lambda/2 50 ohm coax
> section;
>
> O Physically move one set of elements 180 degrees forward or behind;
>
> O Turn one of the driven elements 180 degrees so the loop is on the other
> side of the antenna, but maintain the same electrical connections.
>
> This may (of may not!) help... http://www.g6lvb.com/remotepolarization.htm
>
> It takes a bit of lateral thinking, but once you've figured it out it's a
> bit like learning to ride a bike in that you don't forget, although in later
> years I find one may become a little wobbly.
>
> 73, Howard G6LVB
>
>
> -----Original Message-----
> From: Curt Nixon [mailto:cptcurt@xxxxx.xxxx
> Sent: 02 January 2009 16:50
> To: Howard Long
> Cc: 'AMSAT-BB'
> Subject: Re: [amsat-bb] Question adding RHCP to Cheap Yagi
>
> Hi Howard:
>
> Thanks..I've looked at alot of your info on-line--especially the sub-500GBP
> AO-40 setup.
>
> I guess I still don't get it..if I just feed them in-phase with both
> connections same polarity, what controls RH v. LH?
>
> Or is it RH if the front half loop is to the right and LH if the front
> half-loop is to the left?
>
> Thanks
>
> Curt
>
> Too cold to not get it right on the first try!!
>
>
>
> Howard Long wrote:
>
>> Hi Curt.
>>
>> Either way will work.
>>
>> http://www.g6lvb.com/AO-40%2070cm%20uplink%20antenna.htm
>>
>> I have had superb success with mine, in fact during the days of AO-40
>> I worked the world with it as an uplink antenna with 50W.
>>
>> http://www.g6lvb.com/3A2%20ops.htm
>> http://www.g6lvb.com/dayton_demo_2002.htm
>>
>> 73, Howard G6LVB
>>
>> -----Original Message-----
>> From: amsat-bb-bounces@xxxxx.xxx [mailto:amsat-bb-bounces@xxxxx.xxxx
>> On Behalf Of Curt Nixon
>> Sent: 02 January 2009 15:19
>> To: AMSAT-BB
>> Subject: [amsat-bb] Question adding RHCP to Cheap Yagi
>>
>> Good Morning All:
>>
>> I've been using a 10el version of Kent Britain's Cheap yagi for my
>> 70cm downlink antenna. It suffers from deep fades so I am going to
>> add the second yagi with physical offset to get to RHCP in the x config.
>>
>> Question is:
>>
>> normally I would reverse the coax connections to a dipole driver but
>> this is a hairpin (half of a folded dipole. )
>>
>> Do I reverse the connections as normal? Kents instructions just say
>> offset the elements and feed in phase.
>>
>> Thanks
>>
>> Curt
>> KU8L
>>
>>
>> _______________________________________________
>> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
>> Not an AMSAT-NA member? Join now to support the amateur satellite program!
>> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>>
>>
>>
>>
>
>
>
------------------------------
Message: 3
Date: Fri, 2 Jan 2009 11:30:55 -0800
From: "Greg D." <ko6th_greg@xxxxxxx.xxx>
Subject: [amsat-bb] Re: Question adding RHCP to Cheap Yagi
To: <cptcurt@xxxxx.xxx>, <amsat-bb@xxxxx.xxx>
Message-ID: <BLU133-W5140266434A6F305391B9AA9E20@xxx.xxx>
Content-Type: text/plain; charset="iso-8859-1"
Hi Curt,
For CP you would either have the elements offset and feed them in-phase, or
have them not offset and feed them with the phase delay. You want to create a
spin to the wave as it travels down the boom. I expect doing both would make
a mess out of things.
Greg KO6TH
> Date: Fri, 2 Jan 2009 10:19:23 -0500
> From: cptcurt@xxxxx.xxx
> To: amsat-bb@xxxxx.xxx
> Subject: [amsat-bb] Question adding RHCP to Cheap Yagi
>
> Good Morning All:
>
> I've been using a 10el version of Kent Britain's Cheap yagi for my 70cm
> downlink antenna. It suffers from deep fades so I am going to add the
> second yagi with physical offset to get to RHCP in the x config.
>
> Question is:
>
> normally I would reverse the coax connections to a dipole driver but
> this is a hairpin (half of a folded dipole. )
>
> Do I reverse the connections as normal? Kents instructions just say
> offset the elements and feed in phase.
>
> Thanks
>
> Curt
> KU8L
>
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
_________________________________________________________________
Send e-mail faster without improving your typing skills.
http://windowslive.com/online/hotmail?ocid=TXT_TAGLM_WL_hotmail_acq_speed_1220
08
------------------------------
Message: 4
Date: Fri, 2 Jan 2009 11:33:30 -0800
From: Clint Bradford <clintbrad4d@xxxxxxxxx.xxx>
Subject: [amsat-bb] Re: Ham-Mag
To: amsat-bb@xxxxx.xxx
Message-ID: <CE38C203-BBD8-4C83-B158-302A3B241437@xxxxxxxxx.xxx>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
>> ... The first English issue of the free electronic Amateur Radio
magazine Ham-Mag is now available and features an article on working
satellites with your HT by K6LCS ...
Thanks for mentioning that! As always, the original document will be
posted on the amateur radio pages at ...
http://www.clintbradford.com
Clint Bradford, K6LCS / KAF3359
909-241-7666
------------------------------
_______________________________________________
Sent via amsat-bb@xxxxx.xxx. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
http://amsat.org/mailman/listinfo/amsat-bb
End of AMSAT-BB Digest, Vol 4, Issue 6
**************************************
Read previous mail | Read next mail
| |
