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Reviews Categories | Filters, RF: bandpass, lowpass, highpass, RFI/EMI, etc.. | INRAD Roofing Filter ICOM Pro III Help


Reviews Summary for INRAD Roofing Filter ICOM Pro III
INRAD Roofing Filter ICOM Pro III Reviews: 14 Average rating: 4.6/5 MSRP: $200
Description: This roofing filter can help reduce the third order Intermodulation from multiple strong signals in the 2 to 20 kHz region either side of the tuned frequency. Please see our document titled "A Few Words About Roofing Filters" for more details.


Product is in production.
More info: http://www.inrad.net/product.php?productid=225
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KC3ET Rating: 1/5 Apr 28, 2009 19:15 Send this review to a friend
Have It Installed Professionally  Time owned: months
I recently purchased the 'Inrad IC756 Pro 3 Filter Mod'. Inrad is correct that the installation is not for the average radio amateur. I started the installation, but stopped when it came to the step in which I would have had to remove the R216 SMD resistor from the
RF-A board. I finally found R216 using a Jewelers Loop. It is very small. I also had to use quite a bit of soldering iron heat to get the center shield cover off of the RF-A board. Also, my preparation of the 2 RG174 cables that connect from the RF-A board and the Inrad filter, was not easy, as the cables kept breaking. At this point, I have packed my IC 756 Pro 3 and sent it out to Burghardt for repair and to install the filter. The Burghardt rep told me on the phone that they use a Microscope to work on both repairing the IC 756 Pro 3, and installing the Inrad filter mod for the IC756 Pro 3. I asked the rep at Burghardt to go over all of my work, and to check the IC756 Pro 3 for proper operation. Prior to shipment, I reassembled the IC756 Pro 3. It appeared to work properly, although I am not sure whether the sub receiver is working or not. I will post my results when I receive the IC756 Pro 3, with the Inrad filter installed, when I receive it from Burghardt.

For now, my advice, if you want that filter have it professionally installed. Inrad mentions several companies that can do the installation.
73
 
EA3GEG Rating: 5/5 Dec 25, 2008 09:34 Send this review to a friend
Very good  Time owned: more than 12 months
I installed INRAD filter on my pro III, and the results are very good, the noise and splatters for nears frequecys going down, signal about +25 dB, on 3 or 5 Khz up don't disturb now.
The instalation is a little dificulto, but with pacience don't any problem.
Grettings

Joan EA3GEG
 
K8AC Rating: 4/5 May 22, 2008 15:48 Send this review to a friend
Difficult installation - minor scope effects  Time owned: 0 to 3 months
I chose to install this roofing filter after experiencing the IMD problem during the CW SS in 2007. While I don't have any way to test the results (until next contest season), I trust the info provided by I1ODP regarding the measurements. If you're not confident of your ability to work with the tiniest of surface mount devices, you probably want to avoid doing the install yourself. You need to remove a resistor and connect a discrete capacitor and resistor to the pads left after the removal, and you'll need some good magnification to carry that out. Mechanical work includes the removal of a shield can from the board, drilling two small holes in it and attaching two small coax cables to the shield. The filter board is completely assembled and it is placed in an open space just to the right of center behind the front panel display. The board just sits in the space and can move around if you happen to ship your Pro III, so if you plan to do that you might consider forcing a piece of foam plastic between the board and the frame to hold it in place.

I had heard that the filter had some effect on the spectrum scope display, but observed only a minor effect on signals. At a point approximately 3.3 KHz on each side of the center frequency, I found that the displayed signal peaked about 3 dB over a small range and I determined that by tuning across the calibrator signal while watching the signal height with the vertical scale. The effect isn't noticeable unless you're looking for it with the calibrator or other stable signal source.

The filter reduces the bandwidth enough to affect the fidelity of AM broadcast signals as you'd expect, but it's in the signal path for the main receiver only. If you want to listen to AM with the same fidelity as before, you can use the subreceiver in dual watch mode and adjust the balance control so you don't hear the main receiver.

My rating of 4 considers the difficulty (and high risk) of the installation and the fact that the filter board is not secured in the mounting space. I would not recommend the installation unless you are bothered by the IMD problems of the stock receiver.
 
I1ODP Rating: 5/5 Feb 24, 2008 10:22 Send this review to a friend
A great performer  Time owned: 0 to 3 months
I just measured my Pro III with Inrad roofing filter (nominal 3kHz BW) :
Noise Floor -135 dBm
MDS -132 dBm
Dynamic Range with
2 interfering signals spaced 5kHZ -------------> 95 dB (9+35 on the Smeter) about
2 interfering signals spaced 4kHZ -------------> 92 dB (9+30 on the Smeter) "
2 interfering signals spaced 3kHZ -------------> 82 dB (9+20 on the Smeter) "

Without the roofing filter I measured years ago my Pro III see

http://www.ab4oj.com/icom/ic756pro3/i1odp.html

and close-in Dynamic Range results where :

2 interfering signals spaced 4,4 kHZ -------------> about 80 dB.

Conclusion:
Using narrow VHF roofing filters you improve your Pro III DR (2 sigs spaced 4 kHz) by more than 12 dB .
 
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