Special thanks to Fred Hopengarten, K1VR, for forwarding this summary to the KA9FOX web site!! --------- Begin forwarded message ---------- From: "Alfred J. Frugoli" To: topband@contesting.com Subject: TopBand: Beverage Preamp Summary Date: 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 length. 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. Al, KE1FO, ex. KE6BER --Replies-- 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@mathworks.com -- 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 -- 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 -- 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 -- 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. 73, Charles 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! 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, K1KI frenaye@pcnet.com -- 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. Michael ChristiE, k7rls/4 -- 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. 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. Sid k3sme@usa.pipeline.com -- 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 -- 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, George, K8GG -- The general thought 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. JOhn Farber, KG6I, 1.8-1296 jfarber@sprynet.com --------- End forwarded message ----------