Date: Fri, 11 Feb 94 04:30:38 PST
From: Ham-Equip Mailing List and Newsgroup <ham-equip@ucsd.edu>
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Subject: Ham-Equip Digest V94 #28
To: Ham-Equip
Ham-Equip Digest Fri, 11 Feb 94 Volume 94 : Issue 28
Today's Topics:
386DX/25 PC for sale
Alinco DJ580 and car power
Help: TS430 and SM220 monitor
Intermodulation
KENWOOD TH77E VS STANDARD 720
LOOKING FOR KENWOOD TS-950S OR TS-950SD
RC-1000 Repeater Controller
TS430: 80 M RFI problem
Vertical Antennas (2 msgs)
WANTED: Kenwood TS-950SD or TS-950S
Want Yeasu ft707
Send Replies or notes for publication to: <Ham-Equip@UCSD.Edu>
Send subscription requests to: <Ham-Equip-REQUEST@UCSD.Edu>
Problems you can't solve otherwise to brian@ucsd.edu.
Archives of past issues of the Ham-Equip Digest are available
(by FTP only) from UCSD.Edu in directory "mailarchives/ham-equip".
We trust that readers are intelligent enough to realize that all text
herein consists of personal comments and does not represent the official
policies or positions of any party. Your mileage may vary. So there.
----------------------------------------------------------------------
Date: 8 Feb 1994 15:58:02 -0500
From: ihnp4.ucsd.edu!sdd.hp.com!spool.mu.edu!howland.reston.ans.net!torn!nott!gandalf.ca!gandalf.ca!not-for-mail@network.ucsd.edu
Subject: 386DX/25 PC for sale
To: ham-equip@ucsd.edu
System includes 8MB RAM, 80MB SCSI HD, 5.25 1.2MB floppy and ATI SVGA
video card. Asking $500. If interested, call (609)-424-8700,
x5904 or email bob@gandalf.ca.
------------------------------
Date: 9 Feb 1994 10:42:52 -0500
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!news.intercon.com!digex.net!digex.net!not-for-mail@network.ucsd.edu
Subject: Alinco DJ580 and car power
To: ham-equip@ucsd.edu
My Alinco DJ580 is my only piece of ham equipment and thus I do not want
to do anything that might destroy it. But I would like to be able to
hook it into the car's cigarette lighter to both save the battery and get
more wattage out of it. I have the necessary plug that fits into the DC
in socket on the side of the radio, as well as a plane-jane cigarette
lighter plug. What type of fuse is recommended for this, and is there
any other circuitry that is advisable to connect between the radio and
the car?
Also, I have a 12V 4A regulated power supply powered by household
current. Would the same precautions apply to connecting the radio to it
as would apply to connecting it to the car's power?
------------------------------
Date: Wed, 9 Feb 1994 15:09:20 GMT
From: cs.yale.edu!csusys.ctstateu.edu!white@yale.arpa
Subject: Help: TS430 and SM220 monitor
To: ham-equip@ucsd.edu
Looking for info on how a SM220 Station Monitor would work
with my TS430S HF rig..... I haven't been able to find ANY
information on this. Thx, 73 de N1QVE. Harry.
Email to white@csusys.ctstateu.edu
------------------------------
Date: 6 Feb 1994 00:16:06 GMT
From: qualcomm.com!vixen.cso.uiuc.edu!howland.reston.ans.net!usenet.ins.cwru.edu!odin!trier@network.ucsd.edu
Subject: Intermodulation
To: ham-equip@ucsd.edu
There are a couple of types of interference that people call "intermod"
but only one is intermodulation! The other two that I've seen called
"intermod" are imaging and front-end overload.
Imaging is caused by the frequency-shifting performed in a receiver.
Suppose the mall security is on 464.575, a ham repeater is on 443.175,
and your receiver has an intermediate frequency (IF) of 10.7 MHz. When
you try to receive mall security, the radio will mix the signal from
the antenna with a 453.875 MHz local oscillator's signal, in order to
generate the 10.7 MHz IF it needs for the later stages of reception.
(Subtract 453.875 from 464.575 and you will get 10.7 MHz, assuming I
made no arithmetic errors!) However, the mixer will recieve _any_
signal that is 10.7 MHz away from 453.875. That means it will receive
443.175 as well!
That is "imaging" -- two frequencies for the price of one. In a
narrow-band receiver, a filter on the front end will remove the
undesired signal. For example, a good ham-band radio will filter out
450 MHz on up, removing the mall security from contention. However,
your scanner is inherently wide-band, so it can't filter as well. Lots
of scanners have problems with images.
Front-end overload is simpler: If a signal is too strong, it may wind
up overloading the receiver, making the mixing and filtering moot. The
result is that you hear that too-strong station no matter what. You
may see this on a car radio or a scanner when right next to a broadcast
transmitter. In narrowband receivers, better front-end filters can
help. Notch filters that remove the strong source can also help.
While you may see front-end overload on your scanner, it is fairly
unlikely that is what is happening here with the mall security and the
ham repeater.
Finally, real intermodulation: This gets complex, but not too complex
if you accept the existence of the 10.7 MHz IF in the radio. Suppose
there are _two_ strong transmitters in the area, 10.7 MHz apart. If
both transmit at the same time, no matter what their frequency is, they
may mix inside your receiver's mixer and generate the 10.7 MHz signal
needed by the rest of the radio. Presto -- you hear both, but only
when both are on at the same time. Intermod can also happen if the two
sources are farther apart -- suppose they are 146.00 MHz apart and you
tune your radio to 146.00 MHz. That mixing effect may again create a
signal your receiver picks up. Just as with the last two types of
interference, intermod can be reduced by better filtering in a narrow-
band receiver.
When I've encountered intermodulation, I have heard both signals
simultaneously. Since it happens only when both transmitters are
active, it may come and go strangely. One radio and location I've used
suffers from intermod between a university maintainance repeater and a
pager system. The result? Intermittent squeals of pager tone overlaid
with maintainance radio traffic.
See? It's not as complicated as it seems. It might be worth checking
your scanner's specifications to find out its IF, because that will let
you add and subtract it to see if you are seeing imaging, intermod, or
front-end overload.
Stephen
--
Stephen Trier KB8PWA Dave: [H]as anyone ever met a Zamboni driver?
Other: trier@ins.cwru.edu Mike: The next version of OS/2 will include a
Home: sct@po.cwru.edu Zamboni driver. Let's see Microsoft top that!
(dave@cs.arizona.edu & miked@vnet.ibm.com)
------------------------------
Date: 10 Feb 1994 09:44:34 GMT
From: mvb.saic.com!unogate!news.service.uci.edu!usc!cs.utexas.edu!howland.reston.ans.net!pipex!sunic!EU.net!news.forth.gr!helios.intranet.gr!phaethon!demetre@network.ucsd.edu
Subject: KENWOOD TH77E VS STANDARD 720
To: ham-equip@ucsd.edu
CQ Netters
Does anyone have comparison data for the Kenwood TH77E and the Standard 720
dual band handhelds ???
Which is better ? why ? can either of them turn their TX off automaticly
while being used as repeaters ??
Which has more repeater related functions ??
73's
------------------------------
Date: 11 Feb 94 05:17:00 GMT
From: news-mail-gateway@ucsd.edu
Subject: LOOKING FOR KENWOOD TS-950S OR TS-950SD
To: ham-equip@ucsd.edu
Hi everybody!
I am looking for used Kenwood TS-950S or TS-950SD.
I would rather rig. with manual and carton. Without some trouble!
I hope to get real price. My friend have location in US, now.
Respond please only to my E-mail: rw3aj@glas.apc.org before
20 february.
With the best regards Serge , RW3AJ from Moscow
------------------------------
Date: Mon, 7 Feb 1994 20:25:09 GMT
From: utcsri!newsflash.concordia.ca!sifon!clouso.crim.ca!hobbit.ireq.hydro.qc.ca!barde!vaillan@uunet.uu.net
Subject: RC-1000 Repeater Controller
To: ham-equip@ucsd.edu
Can anybody give me some comments about the RC-1000 Repeater Controller?
It is sold by Micro Computer Concepts in Florida.
Any comments, good or bad, are welcome.
I would like to use two of them to interconnect on demand a VHF and a UHF
repeater.
Regards,
Clem.
73
---
Clement Vaillancourt, | Institut de Recherche d'Hydro-Quebec
Analyste, | Varennes, P. Quebec, Canada, J3X 1S1
Informatique scientifique | Tel:+1 514 652 8238 Fax:+1 514 652 8309
vaillan@ireq.hydro.qc.ca | Radio-amateur: VE2HQJ@VE2CRL.PQ.CAN.NA
------------------------------
Date: Tue, 8 Feb 1994 22:25:48 GMT
From: cs.yale.edu!ccsua.ctstateu.edu!white@yale.arpa
Subject: TS430: 80 M RFI problem
To: ham-equip@ucsd.edu
My TS430 has developed a noise problem between 2.700 and 4.300 MHz.
It is a pulse, that the noise blanker does a good job of suppressing
but the wanted signals also get crunched a bit too much. Does this
freq range have any RFI significance? Thx.....
73 de N1QVE Harry
------------------------------
Date: Wed, 9 Feb 1994 02:00:41 GMT
From: ucsnews!sol.ctr.columbia.edu!math.ohio-state.edu!sdd.hp.com!col.hp.com!srgenprp!alanb@network.ucsd.edu
Subject: Vertical Antennas
To: ham-equip@ucsd.edu
Gary Coffman (gary@ke4zv.atl.ga.us) wrote:
: In article <CKvGDJ.GFv@srgenprp.sr.hp.com> alanb@sr.hp.com (Alan Bloom) writes:
: >Consider a vertical dipole in free space. You could insert a horizontal
: >infinite ground plane at the feedpoint without changing the radiation
: >pattern. Now you have two verticals, one pointing up, one pointing down.
: >Each vertical radiates half the power of the original dipole.
: True because each has half the current that flows in the entire dipole.
No, the current is the same, but the power is halved. There are (at least)
two ways to see this: 1) Only 1/2 the voltage is applied to each 1/4-wave
element. Since power = voltage times current, the power is 1/2.
2) The element is only 1/2 as long. So the same current results in
only 1/2 as much power radiated.
Actually, 2) can be derived from 1). (Left as an exercise for the reader :=)
: >Note
: >that the upper vertical (over a groundplane) can generate the same
: >field strength as the dipole (in free space), but with only 1/2 the power.
: No, I disagree with the way you're saying this. The upper vertical in
: this thought experiment has half the current of the dipole and so generates
: half the field. The ground mirror is supplying a 3 db reflection gain that
: makes up for the lower field produced by the current in the upper vertical.
Nope, see above.
: >Now consider a dipole suspended a half wavelength or more over an infinite
: >ground plane. In some directions, it will have 6 dB gain over a dipole
: >in free space, which gives 3 dB gain over the vertical. In other directions,
: >the field will be zero. If you averaged the radiated power over all
: >directions (half sphere), you would find it sums to the same power as the
: >1/4-wave vertical (also averaged over all directions.)
: True, but gain in the main lobe (what we normally mean when we talk about
: gain) is 2X that of the vertical. And in the real world of lossy ground
: planes that make poor current mirrors, the horizontal dipole has a greater
: efficiency.
But to get the 6 dB gain, the dipole depends on ground reflections, just
as the vertical does. It gets very complex trying to compare ground losses
of ground-mounted verticals versus horizontal dipoles because of the many
variables involved (type of earth, number of radials, height above ground,
vertical radiation angle, etc. etc.). That's why assuming a perfect ground
gives a much more usable standard of comparison.
AL N1AL
------------------------------
Date: Wed, 9 Feb 1994 14:01:42 GMT
From: ucsnews!sol.ctr.columbia.edu!destroyer!gatech!wa4mei.ping.com!ke4zv!gary@network.ucsd.edu
Subject: Vertical Antennas
To: ham-equip@ucsd.edu
In article <CKxpL6.LKB@srgenprp.sr.hp.com> alanb@sr.hp.com (Alan Bloom) writes:
>Gary Coffman (gary@ke4zv.atl.ga.us) wrote:
>: In article <CKvGDJ.GFv@srgenprp.sr.hp.com> alanb@sr.hp.com (Alan Bloom) writes:
>: >Consider a vertical dipole in free space. You could insert a horizontal
>: >infinite ground plane at the feedpoint without changing the radiation
>: >pattern. Now you have two verticals, one pointing up, one pointing down.
>: >Each vertical radiates half the power of the original dipole.
>
>: True because each has half the current that flows in the entire dipole.
>
>No, the current is the same, but the power is halved. There are (at least)
>two ways to see this: 1) Only 1/2 the voltage is applied to each 1/4-wave
>element. Since power = voltage times current, the power is 1/2.
>2) The element is only 1/2 as long. So the same current results in
>only 1/2 as much power radiated.
Ok, apparently I'm not analyzing this case properly. Here's the way
I see it.
Dipole split by infinite ground plane.
|
|
-------/\/\/\/\---o | o---/\/\/\/\-------
E1 | E2
|
|
If we apply drive to E1-E2, equal currents are driven into each element's
impedance. So the halves of the dipole have equal currents flowing in them,
but 180 degrees out of phase. With the infinite ground plane isolating the
halves, one half has half the total current flow.
Gary
--
Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems | we break it. | uunet!rsiatl!ke4zv!gary
534 Shannon Way | Guaranteed! | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244 | |
------------------------------
Date: 11 Feb 94 05:10:00 GMT
From: news-mail-gateway@ucsd.edu
Subject: WANTED: Kenwood TS-950SD or TS-950S
To: ham-equip@ucsd.edu
Hi everybody!
I am looking for used Kenwood TS-950S or TS-950SD.
I would rather rig. with manual and carton. Without some trouble!
I hope to get real price. My friend have location in US, now.
Respond please only to my E-mail: rw3aj@glas.apc.org before
20 february.
With the best regards Serge , RW3AJ from Moscow
------------------------------
Date: 8 Feb 1994 03:04:25 GMT
From: dockmaster.phantom.com!lev@uunet.uu.net
Subject: Want Yeasu ft707
To: ham-equip@ucsd.edu
I want a serviceable Yeasu FT707 HF rig.
------------------------------
End of Ham-Equip Digest V94 #28
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