Mark – Indeed, that I understand. But what can YOU hear in a 10 Hz bandwidth that is intelligible? Or, is it just a matter of being able to discern that there are multiple stations there for a visual display? 73 – Mike
Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ 07731
908-902-3831
From: Mark K3MSB <[email protected]>
Sent: Friday, November 21, 2025 5:51 PM
To: Mike Feher <[email protected]>
Cc: ARC5 <[email protected]>; [email protected]; Military Radio Collectors Association <[email protected]>
Subject: Re: [MRCA] [ARC5] [Milsurplus] Vintage LF/MF Fun with my BC-453B
Hi MIke
Here's a screen capture from my SDR from 17 Nov 2025 0200 EST:
It shows the USB for VQK and HK, both on 332 Kc
VQK is in Washington DC and HK is in Hickory NC.
The USB Frequencies are:
HK 333.018 Kc
VQK 333.028 Kc
That's a difference of 10 Hz.
At my QTH, VQK is a boomer, and HK is weak. Without a very narrow filter, I cannot clearly hear HK.
73 Mark K3MSB
On Fri, Nov 21, 2025 at 4:07 PM Mike Feher <[email protected]> wrote:
Hi Mark – I am curious, what can you possibly hear thru a 7Hz or even a 20 Hz audio filter? Thanks & 73 – Mike
Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ 07731
908-902-3831
From: [email protected] <[email protected]> On Behalf Of Mark K3MSB
Sent: Friday, November 21, 2025 3:28 PM
To: Hubert Miller <[email protected]>
Cc: ARC5 <[email protected]>; [email protected]; Military Radio Collectors Association ([email protected]) <[email protected]>
Subject: Re: [MRCA] [ARC5] [Milsurplus] Vintage LF/MF Fun with my BC-453B
HI Hue
Sorry for the late reply.
I'm blessed to have some friends that keep their eyes out for tuning knobs!
The HP-23 provides 250V B+. For my full up SCR-274N setup, I use the same HP-23 but have a 1K 10W resistor in line to drop the voltage to about 190 to 200V. I'll do that for this setup when I find some time.
The Blue Box under the HP-23 is my 28V supply. I got it at an estate sale for $20. It was originally a 12V supply, but it was nicely constructed and had dual metering. I replaced the 12V transformer with a 28V transformer and added a regulator and pass transistor. I think I can source 5A from it, but in any case it is more than sufficient for any ARC-5 (generically speaking) receiver. I have the output filtered, and it's pretty clean.
The box under the headphones is a Timewave DSP-599zx noise filter / audio processor. I"ve done what I call "iron man" listening -- no external audio processing -- and after doing it a few times I find it's much easier on the ears to be able to adjust the audio bandwidth down to 20 Hz. By the way, the little blue box to its left is a Ratzlaff 7 Hz audio filter! I've had to use it many times with my SDR or modern receivers.
73 Mark K3MSB