TopBand: Beverage Preamp Summary
Alfred J. Frugoli
ke1fo@contesting.com
Thu, 24 Oct 1996 18:39:12 +0000
Here's the summary of information I got from the following question. I should
add that the beverages are planned to be 580 feet in legnth.
Thanks to (in no particular order): KM3T, W1FV, N0DH, K3IXD, KB5UL, W3LPL,
K1KI, K7RLS/4, KB1LN, K3SME, WA3EUL, K8GG, and KG6I.
--Original Message--
I may be putting up a beverage soon, and I'm wondering what your
thoughts are on preamps. Are they necessary? What are the sources?
What are the pros and cons of using/not using? I will most likley
install a single wire beverage for Europe, and possibly one for the
west, both being fed at one point about 100 feet from the shack.
Please reply direct and I'll summarize for the reflector.
Thanks.
--Replies--
Al-
It depends on the length of your Beverage and what band you intend to use
it on. How long can you run your Beverage?
If you run one of the suggested lengths (> 580') you should not need a
preamp, provided you use some reasonable grade feedline (RG-213 or
better). CATV hardline is really good for feeding Beverages if you have
some.
Good luck.....you should make out quite well with that much room to run
Beverages! You're fortunate....
73
Dave
KM3T
--
Dave Pascoe dave@mathworks.com http://www.mathworks.com
KM3T 508-647-7362 FAX: 508-647-7002
--
If you properly impedance match the Beverage to your feedline, and
your feedline is not excessively lossy, which is likely true, there
should be no need for a preamp, at least on 160 meters. It will not
improve your SNR because atmospheric noise is the dominant noise source
at low frequencies. If you have enough antenna gain, which should be
the case with any reasonable Beverage, the atmospheric noise will swamp
out the noise generated internally at the receiver, and a preamp will
only further amplify the atmospheric noise along with the signal. The
absolute signal levels on the Beverage may be down from the transmit
antenna by 10-20 dB, but the SNR will be better. A potential disadvantage
of a preamp is that you could degrade the dynamic range of your receiver
if the preamp's dynamic range is not as good as the receiver's front end.
73, John W1FV
--
Alfred
If your Bevs are in the 500' to 1000' catagorey save your money you wont
find that the preamp does much to improve things in terms of copying
signal in the noise. If your bevrages are shorter then a preamp may help
some.
Dave
N0DH
--
KE1FO:
I have 3 EWEs and a slinkly beverage. My single preamp is in the shack. I
can switch it in and out of the line via a coax switch. MOst of the time the
preamp is out of the circuit.
73, Ed
K3IXD
PVRC
--
Depending on how "hot" your rx front-end is you may or may not like a
preamp. I worked a lot of DX in Europe here without one on my Omni VI.
When I added some EWE's I needed a preamp for them, so I built one. Now I
use it on the beverages also with a lower gain setting. It can be another
possible source for overloading by nearby strong signals. I am using a
Broadcast Band filter ahead of mine. I also built a remote switching system
to use muliple antennas with one feeder. Its easy for rx-only operation.
Good luck and have fun on Top Band. 73, Charles
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
Charles W. Shaw NEW MEXICO
4106 W. Alabama One of Our 50 States is NOT Missing.
Hobbs, NM 88242 (At least, on TOP BAND)
<shawcorj@wtaccess.com> KB5UL
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
--
Hi Al!
I prefer to use a preamp, mainly as a convenience so that the receiver
output level stays constant if I receive on the Beverages or the transmit
antennas. I use the Advanced Receiver Research broadband 20 dB preamp
in the shack with a 160M "LPL Bandpass Filter" in front of the preamp. It
works great!
73!
Frank
W3LPL
donovanf@sgate.com
W3LPL RECEIVING FILTERS
Receive only filters optimized for minimal loss and very high rejection of
frequencies below 75% of the filter center frequency.
These filters use very high "Q" high impedance resonators consisting
of powdered iron core inductors and silver mica capacitors. The resonators
are lightly top coupled with minimum value silver mica capacitors.
C1/C2 and C6/C7 form capacitive voltage dividers to match the input and
output resonators to 50 ohms.
Be sure to use good quality RF connectors (UHF, BNC or N; not phono!)
50 ohms --- C1 ------------ C3 ------------ C5 ------------- C7 --- 50 ohms
| | | | | |
| | | | | |
C2 L C4 L C6 L
| | | | | |
|____| |____| |____|
| | |
| | |
Ground Ground Ground
TABLE OF VALUES
INDUCTOR (all three identical)
Band C1 C2 C3 C4 C5 C6 C7 turns wire size powdered iron core
10 36 47 7 75 6 56 27 8 16 T50-10 BLACK
15 51 62 10 110 8 75 36 10 18 T50-10 BLACK
20 75 91 15 150 12 120 51 13 20 T50-10 BLACK
40 150 180 27 300 24 240 100 18 20 T50-6 YELLOW
80 300 360 51 620 47 470 200 23 22 T50-2 RED
160 600 720 100 1240 100 1000 400 28 24 T50-2 RED
Tune filters by squeezing spreading turns and/or adding/subtracting turns
Nominal 3 dB bandwidth 10% of center freq
Nominal midband loss 1 dB
Attenuation greater than 40 dB at 125% of center freq
Attenuation greater than 60 dB at 75% of center freq
73!
Frank
W3LPL
donovanf@sgate.com
--
For 160 and 80m you probably won't need a pre-amp if you have one more than
250' long. As long as the background noise is audible you won't need
anything more... The only reason I'd consider one is if the Beverage and
'regular' antenna are switched back and forth very often, the pre-amp would
tend to level the signals so you won't blast your ears when switching to the
'regular' antenna...
73 Tom
--------------------------------------------------------------------
E-mail: frenaye@pcnet.com Internet: http://www.akorn.net/k1ki
Tom Frenaye, K1KI, P O Box 386, West Suffield CT 06093 Phone: 860-668-5444
--
Hey Al,
Try the Beverage installation without the preamp for "openers."
If you have a good matching transformer, you may find yuour antenna "hears"
well enough. I have the Beverage Box and leave the preamp "off" all of the
time. The preamp improved the loudness of the signal, sure enough, the
background noise level trailed along too. In that regard it was a tad
self-defeating.
THE LOW BAND MONITOR had an article on the Beverage Box about 18 mos. back.
It had a pretty decent discussion of preamp on/preamp off in it. You may
wish to visit it.
The 100-ft feedline from antenna to shack is no problem, btw. Mine is 200-ft
and no preamp [as stated] is used or particularly felt to be necessary.
GL, they be an interesting "little" antenna, dese Beverages. Sometimes they
are absolutely grand; other times they are [anybody looking?] almost
worthless, hi.
73,
-mike-
Michael ChristiE, k7rls/4
Crawfordville, Florida
--
Howdy Al,
I saw your query on the reflector this morning, then visited your Web
Page. Looks pretty good, too! Thanks for the info you provided on there.
By the way, welcome to New England! I would be as interested in the
preamp question as you, so I'll be watching the reflector to see what
replies you get and I would really appreciate copies of anything pertinent
you get via personal E-mail.
From what I've picked up so far, preamps on beverages seem to be not
needed as long as you have a low loss feedline going to them. If you
plan on trying the EWE antennas, those seem to need preamps at the
antenna due to their short physical size and lack of "gain", as compared
to beverages.
On another note, in your Web Page, I saw that you're looking to operate
during the upcoming contests while awaiting your tower stuff to arrive.
I belong to a small group of contesters in my area and you would be
welcome here anytime. We call ourselves the CTRI (Conn - RI) Contest
Group and are not yet affiliated with the YCCC, but we have discussed
applying to that group. We have built a nice little contest station and you
can "visit" it on our Web Page http://www.riconnect.com/ctri
Hope to hear from you soon, and good luck in the contest!!
de Bob Rogers KB1LN
--
Al, preamps are generally helpful on 160. The true measure of a preamp's
contribution is: Does the received signal increase without an increase in
background noise greater than the signal increase;
Do you get extra sigs now with the preamp inline? These would be the
result of BroadCast Band sigs (BCB) mixing with the 160 sigs and entering
the front end of your rig. There are combo preamps with built in high pass
filters so the BCB stuff gets cutoff; individual BCB filters; preamps
(K2ZJ) which are installed at the antenna; preamps which are installed at
thr rig; Palomar, Advanced Receiver Research and old Ameco PLF-2s and 3s.
Don't bother with the MFJ in my opinion.
Pro of preamp/filter at antenna:
Less signal loss and more? attenuation of BCB sigs.
Con; unless you can remote switch out at the Beverages you will buy 1
preamp per antenna. ZJ's are now about $85 I believe.
If the preamp stops working you lose use of the antenna as there is no
direct connect bypass.
Pro of preamp in the shack:
Switch multiple Bevs. in the shack using 1 preamp!
Easier disconnect in storm- no active components outside.
Easier to try different preamps since all antennas are available in the
shack.
If the preamp stops working you still have the Beverages, un amplified, at
your disposal. With any device at the antenna you don't get that option.
FYI I have the ZJ preamp filter combo EARLY EARLY model and did not
consider it to be robust. Some of the short comings have been addressed I
understand.
I have had the same Ameco old PLF-2 ( metal case) since 1979 and have blown
it up and repaired it many times. It is in daily use.
I bought the MFJ preamp used and it did not work well and sits in the heap.
I bought the ICE preamp and, honestly, it has self destructed TWO times on
its own. I am going to call them and request repair or refund.
Many of the newer preamps use a generic micro amplifier 4 terminal device
which goes from DC to gHz. and there is not enough silicon in the chip to
sustain the static hiccup of a sneeze. Also there is insufficient external
protection in these preamps.
I'll be curious to see what others have to say!
73, Sid.
--
k3sme@usa.pipeline.com
--
Hi Sid,
Well said! I use the palamar in the shack and it works very well. Also
have amico in the junk box for a bakcup HI.
73 Bob WA3EUL
--
Hi Al,
Preamps:
Commercial sources include Palomar & Ameco & someone in 2 land, has
advertisements in QST. Maybe WJ2O?
Best home made one I have seen is from a KD9SV article in Ham Radio a
number of years ago. Sorry I don't have the issue date.
Do you need one?
I think so. I have operated from Montserrat using only the pre amp in
an Icom 740 and 500 ft beverages and heard well. I did have a good
high pass filter, as the local 500KW AM station on 930 would do
unintelligible wonders to a lot of signals otherwise.
Many other places I have operated I needed preamps most of the time.
Only when local AM or power line noise was bad did a preamp not help.
In a 160 contest you need all the European "third layer" signals you
can get. Also the US stations that insist on calling the louder
signals with near QRP power or small antennas are in audible without
a big QSB peak or a preamp. Weak signals or not, a valid QSO is a
valid QSO. If you don't hear them you don't work them!! Without the
preamp you would not get the QSO.
There are some conditions when an external preamp is not needed, but
many transceivers lack the gain to do without on 160. Maybe the
TS-930 in general, and the IC-740 I had were the ones that could get
by. A good preamp is not expensive.
On 80 meters, many transceivers are hot enough with 500 ft beverages
to do OK without a preamp. A lot depends on your location, where the
power lines and local AM broadcast stations are located, etc.
Hope this helps,
73 George, K8GG
--
The general thot I have heard is that if you need a preamp for your Beverage,
it's not long enough. I use both a 500 ft and a 200 ft beverage, and both work
well without preamps. Just be sure to properly feed and terminate them. Best
source for info on doing this is the Low Band DX book by ON4UN. Lots of good
info. GL, 73
JOhn Farber, KG6I, 1.8-1296
jfarber@sprynet.com
--
--
Al, KE1FO, ex. KE6BER mailto:ke1fo@contesting.com or ke6ber@tiac.net
Check out my web page, http://www.tiac.net/users/ke6ber for summaries from the
contest reflector and a growing list of amateur radio links.
--
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