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write your own review of the DCI VHF Filters.
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GM1SXX
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Rating: 5/5
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Feb 11, 2006 07:03
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Superb intermod killer
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Time owned: more than 12 months
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DCI 144-146Mhz (UK) 4 chamber VHF filter.
I have one of the 4 chamber VHF filters.
http://www.dci.ca/graph_145-4.htm
I live in a large town (pop. 85,000)and pager breakthrough was a perennial problem. The 2M band was very noisy until I bought this filter. I now know that 2M is not so bad after all, in fact its actually very good.
All of the problems I had have completely disappeared showing that poor design of the front ends in my radios was to blame.
If you live in a high RF environment I can thoroughly recommend these filters. They are very well made... yes I did do the unforgiveable and carefully took mine apart for a look, although I really don't recommend this. Mine was second-hand so it wasn't such a big deal.
The filter is built from four pieces of square section alumin(i)um extrusions screwed to solid brass top and bottom plates with machined coupling slots between the chambers. The resonators appear to be made of central-heating copper microbore tube and are self-supporting with additional foam tubes tucked in between the edges of the cavities and the resonators for additional support. The earthy ends of the resonators are flattened and soldered directly to the brass baseplate making for a strong and rigid assembly. No capacitors are used in this filter and it has no adjustments, having been factory aligned.
Build quality and performance is superb. Insertion loss is very low indeed. Sweeping the filter using my HP141T SA & HP8444A tracking generator confirms the excellent performance.
These are very fine filters indeed.
I have to give this filter a 5 on all counts.
It is one of my better purchases over the years.
73 Al.
GM1SXX
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KC4PX
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Rating: 5/5
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Jul 8, 2004 11:52
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K4T DXpedition with excellent results
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Time owned: 0 to 3 months
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The K4T DXpedition team (Dry Tortugas) was fortunate to use DCI VHF Bandpass Filters on 2 meters and 6 meters. We had two stations running in the same tent, one on HF, the other on 6 and 2 meters. Both filters were the 4 pole type capable of handling 200 watts. Our first impression was how massive these filters were and very well made. As for operation, we never had a problem. Each station operated without any interference throughout the 4 days on the island. On the HF station, we utilized Array Solutions Bandpass Filters for 20, 40 & 80 meters. When considering a multi-op DXpedition or contest operation, having Bandpass filters on each band is a must, otherwise significant interference and operator annoyance would limit the efficiency and tolerance of each operator. I highly recommend these Bandpass Filters to anyone serious on weak signal and contest operation.
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N1OFJ
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Rating: 5/5
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Dec 10, 2003 12:30
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very pleased
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Time owned: 0 to 3 months
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Purchased a UHF custom rackmounted unit for use as a window filter for a 8 channel receive multicoupler (amateur use). Works as advertised with low insertion loss (confirmed with test eq). Nice steep skirt at band edges. Very pleasant people to deal with. Great bang for the buck. Will consider purchasing other products from DCI for future projects.
Dave N1OFJ
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WB9PNU
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Rating: 5/5
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Jul 8, 2003 15:19
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Worth every dollar
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Time owned: 0 to 3 months
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I am using an Icom 207H duo-bander in my Jeep.
I was experiencing lots of interference from intermod products, pagers, and other sources of rf. In some areas around St. Louis, MO it was almost impossible to hear even the repeaters. Now all is well. I just installed the dual band DCI bandpass filter a few days ago. Wow! What a difference. I haven't heard anything but other hams since installed. DCI filter is very massive, heavy, precision made filter. Worth every dollar I paid for it.
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K5UJ
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Rating: 5/5
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Jun 19, 2003 14:58
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High quality on a ham's budget
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Time owned: 3 to 6 months
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I'm trying to avoid ratings inflation (giving everything a 5) but in this case if it isn't a 5 it's real close as in 4.7.
I purchased the DCI-146-4H 2 meter band pass filter about 4 months ago from AES. I run a packet station to a dx cluster about 25 miles away and I was having trouble connecting. I could have solved the problem by putting up an antenna about 50 feet high (I'm in a river valley) but I get antsy above 30 or 40 feet because of the risk of lightning strikes. Preferring to run a 4 el. yagi lower down with a bit higher power, I worried about the data transmissions getting into nearby TVs and FM broadcast receivers. I figured a band pass filter would keep my end of things clean. Also, today's FM rigs have wide front ends--mine was suffering from a paging system and the filter was cheaper than another rig.
Besides custom filters, DCI makes a variety of filters for 2 m. - 70 cm. with either UHF or N connectors. All are rated at 200 watts and come with attenuation plots.
Mine arrived seemingly undamaged with UHF connectors. The metal work is nice to look at but I worried that in shipping, something inside may have come loose. Not confident enough to put it on the packet station and walk away (thinking I might leave the 30 watt amp working into an open circuit) I put the filter on a dummy load first, and hooked up an swr analyzer to it. As advertized, the swr dropped rapidly from >31 (the maximum the MFJ analyzer displays) very near 144 mhz and rolled around between 1 and 1.3:1 until just above 148 mhz, it zoomed back up again. The supplied swr plot for the filter shows an essentially flat response through the band (~1.07:1). I removed the filter and checked again to see if I was seeing the dummy load swr, and received the same response. My unit was essentially transparent.
The manufacturer's literature says, "The filter's design is four helical resonators with aperature coupling." N connectors are optional.
Mfr's specs.: 144-148 mhz. PB loss < 1 db.
Selectivity -57 db @ 136 Mhz; -43 db @ 156 Mhz
VSWR 1.5:1
Dimensions 12"x3"x5"
Wt. 2 lb 11 oz.
So far, I've detected no out of band interference. You may not need one of these if you have no neighbors close by, or are operating with robust equipment (Motorola for example), otherwise this is a company to keep in mind. They are one of several small companies making high quality products for hams at reasonable prices and filling a demand the big guys won't cover.
Contact information:
DCI Digital Communications Inc.
Box 293, 29 Hummingbird Bay
White City, SK, Canada
S0G 5B0
toll free 1-800-563-5351
http://www.dci.ca
email: dci@dci.ca
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K7NG
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Rating: 4/5
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Dec 1, 2002 23:06
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Great!
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Time owned: more than 12 months
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I have one of the DCI 144-146 MHz and one of the 222-225 MHz filters. They WORK. They are temp stable, don't have too much insertion loss, and the signals that crossmodulate the frontend of my gear just aren't there anymore. It's a little surprising how many of the distant repeater or simplex signals you might hear come right up out of the noise when the RF environment presented to the receiver is rid of dozens of super-strong carriers...
They are a little fragile, so be careful - they are fine in a mobile installation if properly mounted and installed, but if you drop one off a workbench onto a concrete floor it might not be anything like the filter you bought.
73, K7NG
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N8WLG
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Rating: 5/5
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Jun 21, 2002 23:57
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Works as advertised!
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Time owned: 0 to 3 months
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I live within 500 meters of major FM broadcast towers, all with greater than 1MW ERP. Before I added the DCI filter, EVERYTHING had some form of intermod/overload attached to it. Now I can hear a bad filter cap in a repeater 25 miles away! This unit cured ALL my intermod/front end overload problems, 100%! I would recommend these filters to anyone experiencing problems that conventional stubs will not cure. They work. Plain and simple.
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KD4WOV
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Rating: 5/5
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Jan 20, 2001 19:11
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What a filter
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Time owned: 6 to 12 months
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I have a huge problem with intermod. Even my comercial radios get swamped by inter mod. I put a UHF band pass filter in line and no more inter mod. most signals were increased by 3 s units due to the recievers not being swamped. i can now hear stations that were not even detecable.
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KG5U
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Rating: 3/5
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Feb 4, 2000 19:58
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DCI VHF & UHF Bandpass Filters = Outstanding perfo
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Time owned: unknown months
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A year or two ago, I was asked to spec the equipment for a ham station in our Emergency Operations Center at Johnson Space Center. Once the VHF/UHF radios were in place, it was patently and painfully obvious that BP filtering was necessary. Our dual-band vertical antenna was on the Mission Control Center roof in the antenna farm. DCI VHF and UHF filters were purchased and put in place and not a peep has been heard of intermod or any other effects. I bought a VHF BPF for the house and will now be buying a UHF filter now that I have a duo-band VHF/UHF radio. I'm even considering a pair for the car.
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KL7DC
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Rating: 5/5
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Jan 12, 2000 11:29
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They work!
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Time owned: unknown months
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Mega Dittos! It solved my intermod problems on the 2 mtr base station here in Eagle River, AK ( a suburb of Anchorage). Well worth the money. 73.
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