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uBITX AM BCI Filter #ubitx

Nick VK4PP
 

HI All.
I have been working on something:

https://groups.io/g/BITX20/wiki/uBITX-AM-BCI-Filter

It will mount ontop of the board with tape and then tap into the RX chain. between K3 and the 30Mhz LPF...
Thoughts?

John <passionfruit88@...>
 

Hello Nick,

I also need a broadcast station filter. I was also thinking along your line of inserting it in the Rx chain rather than in the antenna circuit so that I can use small toroids and not worry about saturation.

Have you tried the filter as described?

All the best,

73, John (VK2ETA)

Nick VK4PP
 

Hi John,
Not as yet, I have cut some PCB and got some NPO SMD caps and t30-6s ready to go, just have to solder it all up and then remove my uBitx from the casing and install, hopefully in the new few days..
73, Nick, VK4PLN.

Nick VK4PP
 

John, you inspired me: build but not installed yet...

John <passionfruit88@...>
 

Hello Nick,

This is looking very good.

I will try a quick version tomorrow with T68-6 toroids (the smallest size I have handy) in the antenna circuit just to see how much attenuation I get. I am using the same circuit as yours and re-calculated the turns for the T68-6.

If that works I will order some small T30-6 toroids and do the same a you.

Please let me know the results when you wire yours up. I will keep you informed of my results.

All the best,

73, John (VK2ETA)

Nick VK4PP
 

Hi John, Ill get it installed tonight...
However, I do have one already installed using T37-6 and tantalum caps that seems to be working fine. It is on the ANT though, So I am hoping puting this new one on the RX path help with TX power (Marginal I imagine...)

Wanna try SKED on the weekend, say Sunday 7pm on 7177, as per other uBITX skeds?

Cheers. Nick

John <passionfruit88@...>
 

Hello Nick,

I am very interested in knowing what results you get. 

My main objectives in not placing it in the Tx path are to reduce the toroid size and to avoid introducing extra mis-match as I have built the unit in a manpack configuration. So I want to glue the toroids down when everything is working.

As for the QSO, I would like to, but until I replace Arduino nano I have very strong tones in and outside the passband.

So hopefully I will receive the replacement Arduino soon.

All the best,

73, John (VK2ETA)

John <passionfruit88@...>
 

Hello Nick,

I tried the filter in the antenna path and it works very well. So I will order some small toroids and try it in the Rx path when I receive them.

Cheers,

John (VK2ETA)

Nick VK4PP
 

Hi John, 
I've completed the mod in the Rx path, and it is fine business.

No problemo, I even think I have more tx per, but that's most likely due to lowering the noise gate on the ssm2167...

Pics to come...
I got all my little bits from minikits.com.au.
73

John <passionfruit88@...>
 

Hello Nick,

Thanks for the information, I will order the parts and do the same.

Cheers, John

Nick VK4PP
 

My filerf implementation:

Mike Woods
 

Nick

Looks good!   Have you cut tracks or removed parts?  Can you describe exactly where this has been inserted as I want to feature this on the ubitx.net website to help others insert a BCI filter in the RX input line.

73 Mike ZL1AXG

On 3/02/18 3:19 PM, Nick VK4PLN wrote:
My filerf implementation:


--
Mike Woods
mhwoods@...

Nick VK4PP
 

HI Mike and the group.

Yes I cut the trace either side of the new HPF board, exposed a bit of the trace and jumperd onto that.
You need to cut the second trace from the PA side. They are in order:
1: TX pwr to the PA circuits via R89
2: RX path (between K1 and K3 relays. (CUT AND INSERT HERE)
3: TX pwr to the LPF bank.
4: RX pwr to the receive circuit (R18,R38...)

I picked up GND from the 2 unused caps C216 and C210
Filter Details: https://groups.io/g/BITX20/wiki/uBITX-AM-BCI-Filter

73, Nick. VK4PLN

Mike Woods
 

Thanks Nick

I will put up the further details on the news item on uBITx.net

I am sure that your mod will be widely adopted for those of us who are aflicted by nearby AM broadcast stations.

Mike

On 3/02/18 11:40 PM, Nick VK4PLN wrote:

Yes I cut the trace either side of the new HPF board, exposed a bit of the trace and jumperd onto that.
You need to cut the second trace from the PA side. They are in order:
1: TX pwr to the PA circuits via R89
2: RX path (between K1 and K3 relays. (CUT AND INSERT HERE)
3: TX pwr to the LPF bank.
4: RX pwr to the receive circuit (R18,R38...)

I picked up GND from the 2 unused caps C216 and C210
Filter Details: https://groups.io/g/BITX20/wiki/uBITX-AM-BCI-Filter
--
Mike Woods
mhwoods@...