Read Microsoft Word - ASL670RevA.doc text version

The Cushcraft ASL670 50-450 MHz LP Antenna: Assembly, Installation and Review By Phil Salas ­ AD5X Introduction My first introduction to the VHF bands was when I operated 6-meters back in High School in 1965 (I was WA3BCQ then). With a Lafayette HA-650 1-watt AM 6-meter rig and a Cushcraft 6-meter Squalo antenna mounted on my Dad's chimney, I was amazed what I could do on that "magic" band with such low power when conditions were right. I frequently was able to work Cuba and Mexico, and halfway across the country. Recently I've been looking at my IC-706MKIIG (used strictly for portable operation up until now) and have been wondering about those higher frequency bands. So I decided to get back not only 6-meters, but also try 2- and ¾-meters. The Antenna VHF/UHF antennas are small enough to be roof mounted, but multiple antennas for multi-band coverage can still be pretty obtrusive. There is a solution, however, if one considers the log periodic antenna. The log periodic antenna is a broadband antenna that can cover multiple ham bands (see an ARRL Antenna Book for more info). However, nothing is free, so you do give up some gain over separate antennas. As an example, a 3-element 6-meter beam has a forward gain of 8-dBi, whereas a same-length (6-foot) log periodic has a forward gain of 6.5 dBi. I'm willing to trade 1.5dB for a single multi-band antenna! The antenna I settled on is the Cushcraft ASL670. This antenna covers 50-450 MHz, and even looks like a TV antenna. And, it can easily be rotated with an inexpensive TV rotator. The ASL670 specs are listed below. ASL670 Specifications Frequency: 50-450 MHz Power: 300 watts Elements: 14 Gain: 6.5 dBi, 4.5 dBd F/B Ratio: 20 dB SWR: 1.5:1 average 3dB BW H-Plane: 110 ° 3dB BW V-Plane: 80 ° Longest Element: 127 in. Boom Length: 6.75 feet (1.9 m) Wind Surface: 2.52 sq. feet Weight: 11.25 Lbs (5.2 kg) Turning Radius: 6.25 feet Horizontal Mount, 3.80 feet Vertical Mount Antenna Assembly You can download the assembly manual directly from the Cushcraft web site at and review it prior to ordering the antenna. The antenna is shipped in two separate boxes ­ one box contains the booms and elements, and the other contains the remainder of the hardware. Photo "Unassembled" shows all the parts prior to assembly. The ASL670 is very rugged and very well made, with all of the hardware being stainless steel, and the antenna parts all aluminum. The instructions are well written, and the assembly is straightforward. Just pay attention to

the alternating top-bottom positioning of the elements and you can't go wrong. The only problem I had was that the four aluminum "crush" spacers that fit into the two antenna channel "U's" were 0.015 inches too wide too fit, so I had to file them slightly. My total assembly time was about two hours, including 30 minutes to file the spacers. All but the last two pairs of elements are solid rods threaded at the end for adjustment where they attach to the booms. The rear two telescoping element pairs are must be adjusted to the proper length using small stainless steel hose clamps. I did not extend these elements to their full lengths at this time to make the ASL670 easier to carry around. Refer to photo "Assembled" for a picture of the completed antenna prior to installation. Mounting the ASL670 I mounted the antenna on my chimney. To do this, I purchased two pairs of Radio Shack RS15-839 Ratchet Chimney Mounts. Another good mount is the Channel Master Model 9067 chimney mount available from Warren Electronics ( These chimney mounts include galvanized steel mounting brackets and stainless steel straps that wrap around the chimney. I used two pair of mounts, just to give myself some safety margin. I figured that the extra $20 was well worth the extra piece of mind ­ i.e., if one stainless steel strap ever breaks, the antenna won't come down! Incidentally, when installing the mounts on your chimney, wear eye protection and leather gloves, as those stainless steel straps are both springy and sharp! For a rotator, a small TV rotator such as the Radio Shack RS15-1245, the Hy-Gain AR35, and the ECG U105 rotators will work fine. Or check out eBay. I've found similar rotators made by RCA, Gemini, Magnavox, and Channel Master for $20-50 there. All of these rotators use a three-conductor rotator cable. Radio Shack sells 100-feet of 3conductor rotator cable for $13 (RS 15-1150). However, I wound up using some extra CAT-5 cable I had for the 50-foot run necessary in my installation. The ALS670 antenna needs a mast size of at least 1.5-inches in diameter. Since the Radio Shack and Channel Master chimney mounts take mast sizes up to 1.5-inches, I used a 1.5-inch diameter aluminum tube for both the chimney mount and the antenna mast. I purchased a 6-foot long 1.5" diameter aluminum tube from Texas Towers ( Texas Towers has a $25 minimum order for shipped items, but if you buy the aluminum tube, coax, and N-Male connector discussed later, you'll meet this minimum order (Texas Towers also sells the ASL670!). I cut the 1.5" diameter aluminum tube into 4-foot and 2-foot sections. The 4-foot section is used for the rotator support mast, and the 2-foot section is used for the antenna mast. For my feed-line, I used LMR-400 coax. This is a relatively inexpensive, low-loss cable (0.9 dB/100 feet on 50 MHZ, 1.5 dB/100 feet on 144 MHZ, and 2.7 dB/100 feet on 450 MHz). The ALS670 includes a feed cable terminated in a female N-connector. I built a 2-foot piece of RG-8X coax terminated with a PL-259 on one end, and a male N-connector on the other end (9913 N-male solder-on with RG-8X reducer). RG-8X is flexible, and provides the "twist" relief needed for the rotating antenna. I used a UHF "bullet" to attach the RG-8X to the LMR-400 cable. I coated all connectors with Liquid Electrical Tape (available form most hardware stores) to waterproof them.

Finally, use UV-resistant tie-wraps to secure the coax and rotator cables to the mast. As mentioned earlier, I had left the rear two elements of the ASL670 retracted to make the antenna easier to carry on the roof, and install on the rotator mast. After installation, I adjusted the ASL670 rear two elements to their proper lengths. That's all there is to it. Not antenna tuning is required. Photo "Antenna Installed" shows my final installation. Conclusion The Cushcraft ASL670 log periodic antenna covers the most popular VHF and UHF bands. It is compact, easy to assemble, easy to install, and can be rotated with an inexpensive TV rotator. And since it looks like a TV antenna, you probably won't have to put up with too many neighbors complaining about its "ugliness". I'm extremely pleased with the versatility and ease of use of this antenna, and I think you will be too.

Unassembled Antenna

AC5NF critiques AD5X's work

Final chimney installation


Microsoft Word - ASL670RevA.doc

3 pages

Find more like this

Report File (DMCA)

Our content is added by our users. We aim to remove reported files within 1 working day. Please use this link to notify us:

Report this file as copyright or inappropriate


You might also be interested in

Microsoft Word - ASL670RevA.doc