Greg Gortman of Lexington, Kentucky is pleased to offer a variety of high quality MuRata 10.7 MHz IF filters for FM receivers and tuners. MuRata filters are considered by DXers and audiophiles to be the best available. Until now these filters were very difficult to acquire in small quantities.
Descriptions for Available Filters
110 kHz – For serious DX work, this extremely narrow filter is useful for reducing or eliminating adjacent channel splatter and revealing those weak stations next to strong locals. This filter is originally designed for separating stations in Europe where channel spacing is only 100 kHz, as compared with the 200 kHz standard in North America. Insertion loss is listed at 7.0 +/- 2.0 db.
150 kHz Low Loss – This very useful filter is the same value filter used in the super narrow IF setting of the Onkyo T-9090II. This filter has the advantage of a very low insertion loss. Listed insertion loss is 4.5 +/- 2.0 db. The factory super narrow filters in a T-9090II have an enormous insertion loss specification of 14db max, which is common to older filters. Updating older filters with modern low loss ones often yield an increase in signal strength and sensitivity.
180 kHz Low Loss – This outstanding filter is my favorite all around performer because it provides maximum signal strength and excellent sound quality. With the lowest insertion loss of any filter available, listed at 3.5 +/- 1.5 db, analog tuners with old high loss filters really wake up when updated with this filter. It is also wide enough to allow RDS information to pass in most cases. Tuners with 3 or more filters are still quite selective using all 180’s. This filter is an excellent choice in the wide slots of tuners with selectable IF paths.
180 kHz Flat Group Delay – Also called GDT type filters. This type of filter is designed for maximum sound quality at the expense of slightly higher insertion loss. The insertion loss specification is listed at 7.0db maximum, and I find it provides about the same signal strength as a 150 kHz low loss. It is useful for tuners you use for listening to music or news, or, if you are an audiophile DXer. You can also set up a selectable IF tuner for both high quality sound and DX at the same time by using this filter in the wide slots and 150s or 110s in the narrow. The 180 kHz value still provides very good selectivity for capturing distant stations. Many digital tuners use 180 kHz values in the narrow slots from the factory. I also find that Murata 180s provide the same selectivity as Toko 150s.
Ordering information – The cost per filter is $1.50 each. Shipping is fixed at $2.00 for any quantity in the U.S.A. Pay with cash, check, or money order. For European customers, I now accept payment in Euros. I ship these filters via first class mail in a protective bubble wrap envelope. This is the ideal way to ship, as the post office delivers on Saturday. There is no minimum order, no small order/processing fee, and no outrageous shipping or handling fee. To order filters, e-mail to email@example.com, don’t forget to include your shipping address. I will ship most orders immediately, ahead of payment in order to speed the process. Mail your payment for the filters to…
Building filter slopes – Generally you should either use all the same value filters, or progressively narrower filters in your IF path. It is a good idea to have an assortment of filters on hand to experiment with. You should install 3 pin sockets on your circuit board to allow quick and easy filter swaps. I recommend buying 40 pin dual wipe IC sockets from Radio Shack…part number 900-7252 or Assmann dual wipe gold plated 40 pin IC sockets…part number AE9840-ND from Digi-key for $1.63. You will have to cut apart the IC sockets using an X-acto razor saw available from hobby supply houses or sometimes model railroad supply stores. It will require time and a bit of manual dexterity to do a good job. Digi-key also offers 3 pin straight sockets for $.75 each…part number A26245-ND (which I have never used) if you do not want to cut apart a 40 pin IC socket, and don’t mind spending a little more money. The contacts are not gold plated on the Digi-key 3 pin sockets , so you may also have to buy the 40 pin Assmann IC socket as well and extract the individual terminals from both and swap them if you want gold.
MuRata Part Marking Guide