Todayβs OnAllBands video shines a bright spotlight on a company that has been helping amateur operators enjoy brighter, more intelligible, and fully customized audio since its founding in 2002.
DX Engineering is proud to carry bhi Limitedβs real-world-proven, audio-improving amateur radio products available at DXEngineering.com. The lineup includes Digital Signal Processing (DSP) noise-canceling modules, speakers, and headphones; parametric equalizers; audio isolation devices; adapter cables; and audio accessories all designed to help hams enjoy clearer sound that leads to higher contest scores, better emergency communication, more weak-signal DXing QSOs, and stress-free rag-chewing.
In the video below, DX Engineeringβs Paul, KJ8EEP, interviews Graham Somerville, M3ZGS, owner and managing director of the Burgess Hill, England-based company known for its innovative devices that remove unwanted background noise and interferenceΒ for vastly improved speech quality.
In the video, Graham demonstrates the capabilities of the bhi DUAL-IN-LINE DSP noise-canceling module (below), which features an improved algorithm that produces exceptional audio quality in noisy conditions, eight filters for noise cancelation from 8 to 40 dB, and compatibility with both high and medium mono and stereo audio input signals.
(Image/DX Engineering)
Graham also displays the bhi ParaPro EQ20-DSP Parametric Equalizer, which lets you customize the sound of your received audio and boost the audio power to your speakers. The unit, as well as parametric equalizers with Bluetooth, enable you to adjust any specific part of the frequency range, providing greater flexibility and accuracy to set the audio to suit your own hearing.
(Image/DX Engineering)
Read more about the following bhi Limited products in these links from OnAllBands:
Iβve been on the QO-100 satellite for about 7 months now and I have to admit I love it!
Having a βRepeater In The Skyβ that covers a third of the world really is a wonderful facility to have access to however, there is one thing that I find tiring and that is the high level of background noise that is always present.
Even though the signals are mostly 59-59+15dB the background βhissβ is very pronounced and gets very tiring after a while, especially if like me you have tinnitus.
Currently Iβm using a NooElec Smart SDR for the receiver and GQRX SDR software on my Kubuntu Linux PC. This works great but, there is one short fall, there is no DSP Noise Reduction (NR) in the software or hardware.
To fix this I recently invested in a BHI Dual In-Line Noise Eliminating Module. The unit itself is nicely put together and has a good combination of inputs and outputs making it easy to connect up to my MacBook Pro to record QSOs and connect my headphones at the same time.
M0AWS BHI Dual In-Line Noise Eliminating Module
At Β£189.95 plus postage from BHI direct itβs not cheap but, it is nicely put together and comes complete with a power lead and a couple of cheap audio cables. The quality of the knobs and mechanisms is good apart from the little grey DSP Filter Level knob that feels cheap and is very wobbly on the switch below. Iβm not sure how long this is going to last with prolonged use and will most likely need replacing with something a little sturdier at some point in the future.
Overall noise reduction is good but, the audio amplifiers on the Audio Input Level and Line Out Level distort very early on in their range and you cannot get them much above level 5 before distortion starts to appear on the received signal. This is disappointing as my headphones are of reasonable quality and are let down by the distortion creeping in from the audio amplifier in the BHI unit.
Iβve tried altering the levels on the input from the IC-705 and no matter what I cannot get a good audio signal in my headphones without some distortion on the higher frequency ranges.
Overall the device does do what I want, it reduces the background βhashβ considerably reducing the fatigue whilst chatting on the satellite. Below is a recording from a conversation on the satellite showing the noise reduction performance of the BHI module.
M0AWS Example BHI DSP NR Recording
The recording starts with the BHI DSP NR off, at 00:07 the DSP NR is switched on, you can clearly hear the difference. At 00:23 the DSP NR is turned off again and at 00:36 the DSP NR is turned on again. The BHI DSP NR Module is set with the DSP Filter Level set at 3 out of 8 which appears to be the best level to use. Switching to level 4 starts to introduce digital artefacts to the audio which only gets worse the higher the DSP Filter Level goes.
With a setting above level 3 there really isnβt much improvement in noise reduction and the audio becomes progressively more affected by the digital artefacts than it does from the background noise.
M0AWS BHI Dual In-Line Noise Eliminating Module with Icom IC-705 QO-100 Ground Station
The only other problem I have with the BHI Dual In-Line Noise Eliminating Module is that is comes in a plastic case. The case itself is solid and of good quality however, it offers no RF shielding whatsoever and the unit is extremely susceptible to RF getting into the audio chain and then being heard during transmit in the headphones and via the line out connections. For the money I would had expected the unit to come in a metal case that provides proper RF shielding. This is a real shame as it lets the unit down considerably.
As setup in the photo above I am using 300mW O/P on 144Mhz from the IC-705 into a perfect 1:1 SWR presented by the DX Patrol 2.4Ghz Upconverter via some very high quality LMR-400 Coaxial cable from Barenco but, I get terrible RF interference via the BHI unit during the transmit cycle. Considering I am only using 300mW I dread to think what it may be like if I was using a 100w HF radio. This is something I need to investigate further as it really is very annoying.
Moving the unit to a different location in the radio room does help a bit but, doesnβt solve the problem completely. At 300mW RF O/P I really didnβt expect there to be a problem with RF getting into the BHI unit.
Having a proper line-out facility on the BHI unit really is nice as it makes it very easy to connect to my MacBook Pro to obtain good quality recordings of signals on the QO-100 satellite as can be listened to above.
Overall I am happy with the BHI Dual In-Line Noise Eliminating Module but, do wish that more care had been taken over using a metal case instead of a plastic case to protect the unit from RF ingress and better audio amplifiers within the unit that donβt distort/clip so early on in their O/P levels.
Is this the perfect noise reduction unit?
No but, overall it is better than nothing and does help to reduce the background noise to a more acceptable level reducing the overall fatigue during prolonged conversations on the QO-100 satellite.
UPDATE: I tried the BHI unit with my FTDX10 on the HF bands and the RF interference is horrendous, even when using QRP power levels! This device clearly hasnβt been designed to work in an RF environment and the total lack of shielding or isolation lets it down terribly. If you are an SWL then this unit is fine but, if like me you like to monitor your transmitted audio whilst on air through headphones then this isnβt the unit for you. To prove the problem isnβt in the radio shack I put the BHI unit in the house some 30m away powered by 12v battery with nothing connected but a pair of headphones and still the unit suffered from RF interference even at QRP levels.