OCI Olds Communications Inc.
Hello, welcome to the OCI web page.
It is just getting started, so please bear with us as we grow.
My name is Ralph Olds, and many years ago I started the company "DCI" and over the years we made about 25,000 filters. I sold that company in 2007 and have been retired since then.
I have also been a ham since 1960 when I got my license at the age of 15. Ham Radio has played a significant role in my life, from getting good jobs, to building companies and most important, to making many friends.
As you now know, I am once again starting to build filters, and the first filter will be a 2 meter Ham filter to be used mainly to reduce intermod.
Intermod is the mixing of signals to create other signals, and when these fall on the frequency that you want to use, you hear squawks and squeals and voices that you shouldn't hear. This mixing can occur anywhere, but the most common place is in the front end of your receiver.
For example, you have been using your handheld radio with a rubber ducky antenna and it was working well. But you decided that you wanted better coverage and to hear more distant stations, so you put up a good antenna and connect your handheld to use as a base station or put it on a good mobile antenna. Suddenly you hear all sorts of interference. What is happening is that with the better antenna, all the signals from many frequencies are now stronger, and they can't be amplified in the small transistor in the front end of the handheld without causing distortion. This distortion causes the mixing of out of band signals to create interfering signals in the ham band.
A good solution for this problem is a bandpass filter that allows the ham frequencies to pass, but stops signals outside of the band.
I have been in business for most of my life, and one of my guiding principles is to have no surprises for any of my customers. I try my best to tell people what they will get when they buy a product from me so that they clearly know what to expect when it arrives.
In this situation I have difficulties, because how much one of my filters will help you depends on the RF environment in which you will use it. If you live out in the country there are fewer interfering signals and a filter may not be any help at all. If you live in a large city and you have interference when you are chatting around town, there is a very good chance that one of my filters will help reduce the interference. If two signals are very near the ham band edge then the filter won't reduce their strength very much and they may still cause interference even with the filter.
So, my problem is that I can't guarantee that they will work for you. I do guarantee that they will filter as per the specs.
If you have interference, the ideal way to buy a filter is to be scientific about it, and measure all interfering signals and calculate the strength and frequencies of the intermod products to see if they fall on frequencies that you wish to use. You will need a spectrum analyzer, and an intermod calculating program and a lot of work. This approach is usually beyond the average ham's test equipment and knowledge. And, after you have done this, it is only valid for one location.
Another way to decide is to look up old blogs about "DCI" and my name "Ralph Olds" on ham sites to see what others have experienced. I also suggest that you try to borrow a filter to see how it works for you, or get a dealer to let you try one, or just use their return policy.
I hope that by now you understand that I want you to get something that works for you and improves your enjoyment of the hobby. I am not about to start misleading people and selling snake oil at this time of my life.
More about the filters. They are great filters. Good passband loss and good out of band attenuation. The SWR is excellent, and the only materials in the filter are aluminum, copper and teflon, and the gold and silver plating on the coax connectors. They can take quite rough treatment without being detuned, but dropping them from 4 feet could cause detuning.
A good bandpass filter should be part of every receiver front end, but that is not going to happen because they would increase the cost of radios too much.
Don't try tuning them yourself without a network analyzer. I can't do it, and I don't think you can. A spectrum analyzer with a tracking generator and a return loss bridge is the minimum equipment.
If all else fails, and you are just not happy with the filter, return it and I will refund your money. I try to avoid this because it is expensive, and it is easier to just sell it to another ham.
Be aware of another limitation. The filter passes ONLY the 2 meter ham band so if you have a dual band rig for 2 meters and 440 with only one antenna connection, it will not work on 440 with the filter in line. It will also not work if you like to listen to commercial signals outside of the ham bands.
The filters are made to transmitted through. They have been tested to 160 watts with low SWR. I suspect they will handle much more than that, and the specs will be expanded as we get higher power testing equipment.
The filters are available with either UHF or Type "N" connectors.
In summary, I hope you continue to enjoy the hobby, and that my filters increase your enjoyment.
Please keep in touch and let me know your experience.
Ralph Olds VA7NU AA7GY ...