PAR BCST-HPF High Pass AM Broadcast Filter?

[iMONITOR]

I was looking at the PAR BCST-HPF High Pass AM Broadcast Filter.
https://www.universal-radio.com/catalog/filters/4426.html

Is a filter like this necessary if you already have a high-end receiver? I would think it's intended more for less expensive receivers that do not have adequate filtering built in? I'm using an ICOM IC-7600 for my receiver. It's too soon to tell if I have a problem as I didn't get a chance to install my outdoor antenna this fall. I know PAR makes excellent effective filters and I use them with my scanner radios. Can anyone provide some feedback on the BCST-HPF for SWL?

 

[zz0468]

Is a filter like this necessary if you already have a high-end receiver?

It depends on your individual circumstances. If you're nowhere near an AM broadcast station, you might do fine without it.

 

[majoco]

IMHO the first option is to "suck it and see"! As you say, your receiver may have adequate bandpass filtering in the front end and they do tend to go up in octaves, like 2 to 4 MHz, 4 to 8 MHz, 8 to 16 Mhz and so on. There is probably a low pass filter only for below 2MHz or whatever your lowest frequency band is. Often manufacturers build in an attenuator into this filter to prevent BC band breakthrough or cross-modulation which is a pain if you want to do some VLF DX. If you don't have any BC QRM then you can disable this attenuator - after the warranty period of course!

 

[ka3jjz]

The obvious question to ask is what radio and antenna are you using? If you are in or near an urban area and are using one of the SDRs like a SDRPlay, you might well need it. There's only one way to find out and that's to try it without the filter and see what happens. You will not damage anything but your ears (heh)

Mike

 

[iMONITOR]

The obvious question to ask is what radio and antenna are you using? If you are in or near an urban area and are using one of the SDRs like a SDRPlay, you might well need it. There's only one way to find out and that's to try it without the filter and see what happens. You will not damage anything but your ears (heh)

Mike

I'm using an ICOM IC-7600 transceiver as my receiver. As mentioned in my OP, it's too soon to tell if I even have a problem at all, as I didn't get a chance to setup and outdoor antenna this fall (due to open heart surgery in September). I did order a MFJ-1886 receive loop antenna to play with indoors this winter, so we'll find out soon.

WWJ AM is 50,000 watts but is about 70 miles away from me.

 

[ridgescan]

I bought the high and low pass PARs. I needed the LPF on the R75. I haven't deployed the HPF but given there are at least 4 MW flamers within 7 miles of me, I'm dumb for not doing it yet, even with my R8600 on the Wellbrook. I just bought the HPF and neglected it 'till I read your thread just now. I will get it going when I get time and report here any differences in HF

 

[WA8ZTZ]

The 5KW daytimer on 1030 in Sterling Heights will be the strongest AM signal received at your location. All the flamethrowers are located downriver.

FWIW, ARRL did an extensive review of your rig in the Nov 2009 QST... the RX dynamic test numbers look good.

My guess is that given your rig, antenna, and location you probably will not need the filter. However, if you feel that you need the filter, go for it, PAR makes good stuff.

 

[nanZor]

Love the PAR filter - used it in several projects.

You can't go wrong - even if you don't need it now and it sits on the shelf for a few years, there's nothing really to degrade, so it is a great tool to last basically a lifetime for when you DO need it.

 

[ridgescan]

I tried the HP filter on the Wellbrook to the R8600. It basically cut out all SW signals. I put it ahead of the antenna interface-I wonder if that's wrong? Maybe I need to put it after the interface just ahead of the antenna switch? Maybe because it's an active antenna is why this happened.

 

[nanZor]

My PAR is out on loan across the country (need to get another one since that appears to be a permanent loan), but I never did a dc continuity check through it to see if it would pass dc, or if there is a cap inline...

I don't know how you are ultimately powering your loop, but is the par blocking dc?

 

[ridgescan]

My PAR is out on loan across the country (need to get another one since that appears to be a permanent loan), but I never did a dc continuity check through it to see if it would pass dc, or if there is a cap inline...

I don't know how you are ultimately powering your loop, but is the par blocking dc?

Forgive me for not knowing how to answer that question, Hz. But I can tell you the Wellbrook is powered by its factory 12v power supply.
How do I know whether the loop is "blocking DC"?

 

[nanZor]

Ah, I was just wondering if the Wellbrook is being sent its power through the coax, and the par is using a cap **perhaps** which blocks dc - I never opened mine up.

But if you are running a separate power lead to it, then pay no attention...

 

[ridgescan]

Ah, I was just wondering if the Wellbrook is being sent its power through the coax, and the par is using a cap **perhaps** which blocks dc - I never opened mine up.

But if you are running a separate power lead to it, then pay no attention...

OK now I follow ya. The "antenna interface" here inside the shack is where the 12v supply plugs into, and yes, the 12v runs up the coax to the "amplifier" at the loop.

 

[iMONITOR]

My PAR is out on loan across the country (need to get another one since that appears to be a permanent loan), but I never did a dc continuity check through it to see if it would pass dc, or if there is a cap inline...

I don't know how you are ultimately powering your loop, but is the par blocking dc?

The MFJ-1886 has a preamp built-in a small enclosure at the base of the loop. It's powered via a supplied MFJ-4116 Bias-T through the coax cable.

 

[prcguy]

I have a couple of old I.C.E brand 1.8MHz high pass filters that do a great job of keeping AM broadcast out of stuff and they pass DC. These show up cheap on Epay here and there.

Another thing to consider with an active antenna is its amplifier might be way more susceptible to IMD and overload than the Icom R-8600. In this case placing an AM BCB filter after the antenna would be like closing the barn door after the horse escaped.

 

[jwt873]

I was looking at the PAR BCST-HPF High Pass AM Broadcast Filter.
https://www.universal-radio.com/catalog/filters/4426.html

Is a filter like this necessary if you already have a high-end receiver?

I'm running an IC-7600. I live near a major center with half a dozen BCB stations. I've never had any issues because of their proximity when listening to HF. (I use an 80 meter inverted vee and a 3 element Yagi for 20 meters and up)..

On the other hand they cause all sorts of problems in the 100 kHz to 500 kHz range when I'm using my Wellbrook loop. I built a low pass filter to eliminate all the BCB crud so I can listen to the aircraft non directional beacons without interference.

 

[ka3jjz]

That's not a real surprise. LW is very much treated like an afterthought in the US because no US broadcasting occurs there. So it doesn't get the good filtering and front end protection that other bands do.

Mike

 

[ridgescan]

I have a couple of old I.C.E brand 1.8MHz high pass filters that do a great job of keeping AM broadcast out of stuff and they pass DC. These show up cheap on Epay here and there.

Another thing to consider with an active antenna is its amplifier might be way more susceptible to IMD and overload than the Icom R-8600. In this case placing an AM BCB filter after the antenna would be like closing the barn door after the horse escaped.

That's not a real surprise. LW is very much treated like an afterthought in the US because no US broadcasting occurs there. So it doesn't get the good filtering and front end protection that other bands do.

Mike

My R75 in the living room going to the 100' endfed with 9:1 PAR box has the PAR LPF inline because as ka3jjz stated, that rig and the R71a when it ran on the Wellbrook, both suffered terrible IMD from MW in LW.
However, the R8600 to the Wellbrook loop, with no help from a LPF, suffers no MW IMD at all in LW. What a radio So prcguy is also correct that there likely is no need for this HPF either with the R8600.

 

[devicelab]

So prcguy is also correct that there likely is no need for this HPF either with the R8600.

Very bad assumption sir. If you live near AM BCB stations that pump out 50,000 watts then you should seriously invest in a filter.

Here's my Clifton HPF filter:

Here's a screenshot of DC - 10 Mhz without the filter:

Now, here's the same range but WITH the filter:

 

[ridgescan]

I already have the PAR HP filter as indicated in posts #6 and #9.
Are those screenshots from the R8600? And is this on the Wellbrook loop?