Other SOTA sites: SOTAwatch | SOTA Home | Database | Video | Photos | Shop | Mapping | FAQs | Facebook | Contact SOTA

FT-857D CW Question


#1

Here is a question for you FT-857D CW users…

Does the DSP CW peaking filter suffice or do you need the optional narrow filter (or INRAD equivalent) as well?

Please discuss.

73 Marc G0AZS


#2

In reply to G0AZS:

Marc,

I purchased my 857D with a 500Hz filter fitted. Personally I find the DSP useful on top of the filter, probably on account of the fact that my other rigs are fitted with 300Hz filters. I havent tried the DSP without the CW filter, so cant comment on whether it alone is sufficient. I did however work CW for over 20 years with only an SSB filter and the IF shift facility on my TS-130V and coped - maybe the ear-brain filter had a lot to do with that!

73, Gerald G4OIG


#3

In reply to G0AZS:

In the tradition of SOTA responses whether you do not have experience of the question being asked, let me say this. I have a TS570 HF receiver with DSP. In the 570 the DSP operates on the AF signal, i.e. after demodulation. The DSP offers CW bandwidths down to 50Hz and it works. Then you go on 40m and some big signal appears and your weaker CW signal in the DSP bandwidth disappears completely because the big signal blasts through the wide IF and kills the AGC. Without the add-in CW filter it was pretty useless.

So if the DSP works on the IF you shouldnt need an analog filter. But if its AF based like the 570 then it will not be very effective on crowded bands. The TS870 used IF DSP filtering and (receiver improvements aside) is orders of magnitude better than the 570. Of course these are older radios and many sets, even budget ones, now sport IF DSP or have it as an option.

The only part of the AF DSP in the 570 that is effective is the CW noise reduce function. That does peak up CW signals and is effective regardless of the IF or AF bandwidth. The DSP auto notch is very good too.

Andy
MM0FMF


#4

In reply to G0AZS:

The FT-857D is absolutely pants on CW without the narrow filter in that you can be listening to a good clear, but not too strong CW signal and it suddenly completely disappears when a stronger CW signal further up or down the band appears. DSP does not solve the problem.

I have yet to invest in the CW filter (because of cost)for my 857/817, but I do have it fitted in my IC-706, and very effective it is too.

Mike G4BLH


#5

In reply to G0AZS:

I have a 300Hz filter on my FT-857 and I much prefer it to the DSP mainly because I find that it is easier to use and the required signal sounds sharper.

However, it is worth knowing that if you have the filter switched in on cw and you then change mode to ssb, it is still switched in as I found out to my cost on a recent activation.

73
Nick G4OOE


#6

In reply to G4OOE:

I have a 300Hz filter on my FT-857 and I much prefer it to the DSP
mainly because I find that it is easier to use and the required signal
sounds sharper.

Just to add a note to my earlier post in the light of Nick`s comment above - I definitely prefer the 300Hz filter in my 817 to the 500Hz filter in my 857. To compensate on the 857 I use the DSP with the 500Hz filter switched in for CW. The combination works well for me, but I still think I made a mistake in not having a 300Hz filter when I purchased the rig.

However, it is worth knowing that if you have the filter switched in
on cw and you then change mode to ssb, it is still switched in as I
found out to my cost on a recent activation.

That`s strange - mine switches over to the SSB filter when I change mode from CW to SSB. Looks like a menu issue Nick - no doubt some manual-guru will advise.

73, Gerald G4OIG


#7

Many of the problems with audio filtering can be reduced or eliminated by either incorporating the filter within the AGC loop or, more easily, by switching the AGC off and using a manual gain control. Hardly any of my home made rigs have AGC of any sort and I seldom miss it.

73

Richard
G3CWI


#8

In reply to G3CWI:

Switching the AGC off is not always possible on some radios though Richard. You cant disable it on the TS570, only switch between fast and slow. Im sure you can on disable it on the 817 which suggests the 857 will be same.

Andy
MM0FMF


#9

In reply to MM0FMF:

You can`t disable it on the TS570,

However, this appears to provide a solution:

http://md0mdi.com/pages/ham_radio/radios/kenwood/kenwood_ts-570d_mods.html

Not tried it myself yet, but doesn`t look too difficult and is easily reversible.

Rick


#10

In reply to MM0FMF:

In reply to G3CWI:

Switching the AGC off is not always possible on some radios though
Richard. You cant disable it on the TS570, only switch between fast and slow. Im sure you can on disable it on the 817 which suggests the
857 will be same.

Andy
MM0FMF

This is so. Multifunction row “L”, button B enables/disables AGC. On the 817 it is multifunction row 8, button B.

73

Brian G8ADD


#11

In reply to G8ADD:

I was fairly sure you could Brian.

In reply to M0RCP:

Thanks for the link Rick. The AGC mod is quite well known but you either use AGC fast position as AGC off and lose fast or have to add an addition switch somewhere. I was going to do it to my 570 when I was more interested in digital ops. That was when some eejit on 40m with some uber-splatery loud signal could spoil all the fun. However, I found a 270Hz CW filter on offer locally for £15 (read that price and weep!) so I jumped at that. In menu set A the filter is operated as a CW filter and in menu set B it is operated as an SSB filter. That gives me the ability to use it on digimodes if I want and the AGC problem is no longer a problem.

Back to your question Mark, yes you need the filter. Second hand £70-75 is typical. The new price is quite eye-watering and so second hand filters are not on sale for long!

Andy
MM0FMF