AOR 7030+ filters

[carlos2008]

Not long time ago I got a a second hand AOR 7030+ receiver, well used but working as it should be.

An excellent receiver, it came with a 2,4 Khz crystal filter fitted and the rest of filters are Murata's ( CFW455HT 6 Khz (6.8 Khz) , CFW455IT 4 Khz (5.1 Khz) and the 9,5Khz)
Since I am mainly interested in AM DX'ing I find these filters a bit wide, in fact Murata filters it is said that the 455HT even reach the 8 Khz wide, they are not pretty accurated in reality.

I have been thinking about replacing the HT or IT filter with a 6 Khz Collins mechanical filter but I have some doubts whether with this filter I will beable to listening those weak signals more understable. From your point of view, or if anybody has one fitted, would you recommend me this option or it would be silly wasted of money? Any significant improvement in getting more readable signals?
Thanks in advance.

[Nick_B333]

I find that using the SSB filter in either USB or LSB to resolve MW stations works best as it allows you remove the interfering sideband. Very useful when you are dealing with weak American stations on 10kHz channels and strong Europeans on 9kHz channels.

I also have a 7030+ with a similar filter line-up, which I've owned since 2000. I replaced the Murata CFK455K with a Kenwood 2.4kHz filter but I've not tried any of the Collins filters, maybe someone else can advise on those.

[carlos2008]

Thanks for the reply,
I would keep the 455HT only for pleasure listening but I think that the stock Murata filters are not appropiated for serious DX,ing. It is said that the Collins have narrower skirts in selectivity, sounds as a communications receiver.

The AOR that I have purchased has a Murate 3 Khz metal case filter filter ,CFK455J, but I find it useless,maybe a 4 Khz filters would habe been a better option.

Before doing nothing,any help and advices are very wellcomed.

[Bazz4CQJ]

There are always very many different ceramic filters like the Murata one for sale on eBay. The problems are that (i) most of them are more than 4kHz wide (ii) many type numbers show up which cannot be found on the net, so data not available.

If you spend some time sifting through the many listings, you may find some around 4kHz. Please report back if you do .

B

[carlos2008]

The main issue with ceramic filters is that the bandwidth is wider than the specification says,it is not rare to see reports that a 6 Khz Murata (nominal) reachs beyond 8 Khz.
Since I have the F124 daughter board installed the big difference would be a crystal filter (6 or 4 Khz) but I mailed INRAD and they do not manufacture them anymore.

[Radio Wrangler]

Originally Posted by carlos2008

I have been thinking about replacing the HT or IT filter with a 6 Khz Collins mechanical filter but I have some doubts whether with this filter I will beable to listening those weak signals more understable. From your point of view, or if anybody has one fitted, would you recommend me this option or it would be silly wasted of money? Any significant improvement in getting more readable signals?
Thanks in advance.

The Collins mechanical filters are all now getting old and are suffering from rotting foam in their internal supports. You may have difficulty finding a good one.

David

[Nick_B333]

Originally Posted by carlos2008

The main issue with ceramic filters is that the bandwidth is wider than the specification says,it is not rare to see reports that a 6 Khz Murata (nominal) reachs beyond 8 Khz.
Since I have the F124 daughter board installed the big difference would be a crystal filter (6 or 4 Khz) but I mailed INRAD and they do not manufacture them anymore.

I presume you ran the filter calibration routine from the menu when you installed your new filter and didn't see the expected bandwidth displayed? This is quite normal and the AOR service notes mention this. If you are listening to an AM broadcast station through a narrow filter in AM mode, you may have to experiment with offsetting the PBS to improve the quality of the audio. The internal speaker isn't the best either, nor is the rear panel external speaker connector so I use an amplified speaker connected via the front panel headphone jack.

I replaced the Murata CFJ455K14 with a Kenwood YG455S-1 on the FL124 which improved the audio quality for SSB and ECSS AM. This is my configuration -
YG455C-1 0.7kHz
YG455S-1 2.2kHz
CFK455I 3.3kHz
CFK455K 4.5kHz
CFW455HT 6.2kHz
wide 9.5kHz


Some other AR7030 resources you may find useful if you haven't aready found them -

AOR UK no longer exists but the service bulletins are all available at
http://www.aorja.com/support/bulletin_ar7030.html

The AR7030 mailing list and archives can be found at
http://mailman.qth.net/mailman/listinfo/ar7030
It's email-only and very quiet these days but the archive does go back to 2002. You'll need to subscribe to the list to access these.

73

[carlos2008]

Originally Posted by Radio Wrangler

The Collins mechanical filters are all now getting old and are suffering from rotting foam in their internal supports. You may have difficulty finding a good one.

David

They exist in 4 and 6 Khz and 500Hz, a bit pricey but they are brand new:
https://www.truckerswereld.nl/aor-mf-4/
https://www.truckerswereld.nl/aor-mf-6-collins-filter/


Yes, I ran the filter calibration. I have this 2,4 Kz crystal filter for SSB
purposes, it works excellent, since then the CFJ455K14 is useless I like the bass tone though:
https://www.hspshop.it/epages/167668...ectPath=/Shops
/167668/Products/AORXF45524

Thanks for the link, I have already made the subscription.
These text files are very helpful as well:
https://www.radioamatore.info/attach...old7030txt.pdf

The 4Khz filter seems interesting, the stock filter indicates 5,5 Khz maybe a Collins replacement would be nice too.

[carlos2008]

Originally Posted by carlos2008

They exist in 4 and 6 Khz and 500Hz, a bit pricey but they are brand new:
https://www.truckerswereld.nl/aor-mf-4/
https://www.truckerswereld.nl/aor-mf-6-collins-filter/


Yes, I ran the filter calibration. I have this 2,4 Kz crystal filter for SSB
purposes, it works excellent, since then the CFJ455K14 is useless I like the bass tone though:
https://www.hspshop.it/epages/167668...ectPath=/Shops
/167668/Products/AORXF45524

Thanks for the link, I have already made the subscription.
These text files are very helpful as well:
https://www.radioamatore.info/attach...old7030txt.pdf

The 4Khz filter seems interesting, the stock filter indicates 5,5 Khz maybe a Collins replacement would be nice too.

photo

[G0HZU_JMR]

I've still got quite a collection of the classic Murata 455kHz filters here. At work, I did a fair bit of receiver design work in the 1990s and I still have my stash of filters. I still have some of the 455D, 455E, 455F, 455H and 455J filters here although they are all about 30 years old now. Some are still sealed in the parts bag. I can post up some VNA plots of the real filters if that helps?

When the 7030 was first released, I got to speak to John Thorpe the (AOR7030 designer) on the phone as the company was interested in the front end design of the 7030. John authorised AOR to send me lots of factory test and service info about the 7030 and the 5000. I think I may still have some of it. Sadly, I've never had the chance to use a 7030 receiver but I know the performance is very good.

[Nick_B333]

Originally Posted by G0HZU_JMR

I can post up some VNA plots of the real filters if that helps?

I'd be interested to see some and gain some insight into how to test them as I have a few filters and I'm curious to know if they deteriorate over time - but I only have a NanoVNA and I'd like to ensure I get the source and termination impedances correct.

Originally Posted by G0HZU_JMR

Sadly, I've never had the chance to use a 7030 receiver but I know the performance is very good.

RF performance is excellent but compared to some of JTs earlier Lowe designs the menu system can be a bit daunting.

[G0HZU_JMR]

I've got some recent 2 port s-parameter data using a VNA if that helps?

The data only covers 405kHz to 505kHz so make sure you set up any simulator settings accordingly.
I've had to change the *.s2p extension to *.txt to allow the files to be uploaded. It should be possible to experiment with matching networks to find the optimal termination impedances.

Apart from the J version, all of the filters show fairly poor stopband performance when matched. I did mean to measure them all again on a wider span to see if there were any other spurious responses.

[G0HZU_JMR]

Here's a couple of plots after a matching network is added. The plots are for the 455H and 455J versions. Neither of them look that great to me.

I used quite a low source power for the VNA and this partly explains the noisy stopbands. I could also have used a narrower RBW to improve this, but the plots are still useful I think.

[carlos2008]

Originally Posted by G0HZU_JMR

Here's a couple of plots after a matching network is added. The plots are for the 455H and 455J versions. Neither of them look that great to me.

I used quite a low source power for the VNA and this partly explains the noisy stopbands. I could also have used a narrower RBW to improve this, but the plots are still useful I think.

Interesting plots.

Well, I have just finished reading all post in the AR7030 mailing list and AOR's advice is no replacing none of the filters with Collins mechanical filters, according a response of Richard ,a worker of AOR. On the other hand, a couple of SWL,s says the opposite.

I paste the posts, maybe they are a big long:


>if i wanted extra filters ??
>Would the Collins filters really make a difference. ?

The Collins filters are 'mechanical' and have a flat 'nose' and 'steep
shoulders' at the top of the filter plot. This results in an abrupt
filter edge (coupled to relatively steep sides), some people like the
sound of this characteristic, others find it harsh.

However, the 'skirt' selectivity is poor below -60dB, the filter quickly
widens to infinity. For most receivers this would not be noticeable due
to the onset of reciprocal mixing), but when used in the AR7030, the
excellent low noise of the oscillator means that the skirt degradation
would prematurely limit the ultimate stop band performance of the
AR7030. The ultimate performance of the metal cased Murata CFJ455K14 is
actually better than the Collins filters.

The only way to improve on the standard filter is to go for a CRYSTAL
filter such as the AOR XTAL2.4 mounted on the optional FL124 daughter
board. This would provide even better ultimate stop band then the radio
itself. The XTAL2.4 is only available as a DIRECT item from us in order
to keep a lid on the price, we have just one unit at GBP 79.00 inc VAT,
the FL124 board is extra at GBP 24.99 inc VAT. We would not make a
'fitting charge' if ordered with a new set.

As you do not envisage heavy SSB use, it may be worth sticking with the
original filter. It is very usable for ECSS use (using SSB to monitor
AM in order to avoid adjacent channel interference). The XTAL 2.4
filter would provide a slightly wider bandwidth by 100/200Hz.

>Would 2.5 kHz Collins give me better SSB than the Standard 2.2 filter ?

No, a different sound and similar bandwidth to the XTAL2.4 but worse
ultimate stop band (see above).

>Would the Murata 3.0 kHz be a better choice for improving SSB
>performmance ?
>Is the Standard 4.0 ceramic metal cased so good that Collins 4.0 would
>be meaningless ?

The Murata CFK455J filter is already fitted in the PLUS receiver, we
refer to it as the narrow AM filter (its displayed bandwidth is
typically around 3.8kHz). The Collins MF4 is almost identical in
bandwidth, but sounds different. It can be used as a very wide SSB
filter, my guess though is that you will use it as am AM filter.... you
can use any filter in any mode.

The optional CFK455I 4.0kHz filter displays / sounds almost identical to
the standard plastic package 5.5kHz filter... although its stop band
would be marginally better (but less important / less noticeable for
wider filters).

>And therefore the Collins 6.0 would be a better supplement for improved
>AM/SW. ?
>Or would the Collins 4.0 + 6.0 be the ideal solution ?

Personally I would stick with the 'smooth' sound of the standard filters
for AM monitoring, the Collins can sound a bit crunchy (but some folk
like it).

Consider the following:

1) 2.2kHz - stick with the standard CFJ455K14

2) 3.8kHz - stick with the standard CFK455J

3) 4.8kHz - consider the optional CFK455I in place of the 5.5kHz filter
or fit it in addition

4) 5.3kHz - standard filter, could leave it in place but would be
similar
to 455I

5) 6.5kHz - for local strong signal fidelity, we could fit the 6.5kHz
filter
from the standard (not PLUS) unit to provide a wider
spread
of filter choice... there would be no additional charge
in specified at the time of order.

6) 9.5kHz - this is the NFM filter and cannot be changed (firmware
coded)




From ar7030@mailman.qth.net Sun Jun 30 19:07:04 2002
From: ar7030@mailman.qth.net (Bertoglio & Ferraz)
Date: Sun Jun 30 18:07:04 2002
Subject: [AR7030] Filters in 7030
In-Reply-To: <20020630163232.49867.qmail@web10101.mail.yahoo.co m>
References: <018501c2204a$63d3f860$532ffd3e@default>
Message-ID: <5.1.0.14.0.20020630210232.04b5ae00@popmail.libero .it>

Dear friends,

I am in list since long time but I never write anything because my english
is bad, sorry.
I and my friend (Paolo) have two 7030s and during the last 4 years we made
some filter experiments (and spend much money), so I hope our experiences
will be usefull.
But what is the best, speaking about radio? We think the best is to extract
more informations from noise. And we think that this is fundamentally a
personal point of view, every person have personal taste (for example, many
people like a certain grade of muffle sound, others, as me, like crisp and
sharp sound responce).
We tested filters on amateur transmissions (my speciality, I am an SWL and
thanks to my 7030 I was able, during last four years, to obtain
confirmations by about 300 DXCC country in SSB), utility with Code 3 and
Winmix decoders (the Paolo's speciality) and on broadcasting bands, in
particular on tropical bands.


We purchased two SSB optional filters: Collins nominal SSB 2.5 kHz
(actually 2.3 in my 7030) and AOR nominal 2.4 kHz crystal filter.(actually
2.2 kHz on Paolo's 7030) in order to replace the standard Murata CFJ455K14.
We tested these filter in one receiver in the same time. Well, between AOR
crystal and the very good standard Murata ceramic filter we was not able to
found any difference!! Not difference in selectivity also in strong OM pile
up, not difference in audio responce!! Seems that these filters are the
same filter. For this reason we should to open the radio and plug out the
Crystal filter in order to recognize the filter in use. It's an astonishing
result (in particular for Paolo that spend much money to buy it...).
Collins mechanical is different: the audo responce is much crisp and sharp.
It's true, with this filter the splatters are a little more but also in
very interfered conditions it is able to get more informations from noise.
Murata and AOR crystal are more muffle. So I purchased Collins and I like
it very much during contest or Dx expeditions listening. If there is an
audible signal Collins help me very much to understand weak QSO.

I and Paolo purchased also the Murata Data nominal 1.0 kHz filter CFJ455K8
in order to increase utility reception. Well, this flter is 1.5 Khz in our
7030s so it's too large for many transmission code and too narrow as narrow
SSB filter (in SSB is very effective but it's too muffle).
This month I purcahsed, for narrow SSB, one JRC nominal 1.8 kHz crystal
filter (JRC CFL 218A) but actually in my 7030 it's a 1.6 kHz. It's is very
effective on strong interference but at the price of a muffle audio (but
better then Data Mutara ceramic) so, normally i use Collins SSB and i
switch on JRC filter only when it's absolutely necessary.
I think that for good data reception the best will be the JRC Crystal 1.0
kHz nominal (JRC CFL 233).

For narrow CW recepton I purchased Kenwood crystal nominal 250 Hz (YG
455CN-1) that actually is displayed as 0.5 kHz in my 7030. It's very good
and I think that it's more selective than the displayed passband.

We also replaced the poor nominal 3.0 kHz Murata ceramic filter CFK455I
(displayed as 3.5 kHz) with Collins nominal 4.0 kHz (also displayed as 3.5
kHz): the selectivity is much better and audio responce is another things!
For AM Dx it's a very good choice! Very crisp and sharp audio but with good
bass responce also, abosolutely not muffle.

It's all for now, I hope usefull.
Excuse my english and my long mail

73 de Alessandro
SWL I1 4851/TO

[Radio Wrangler]

Your english is fine.

These filters are all 'coupled resonator' types. They use the impedances presented to them by the adjacent circuits of your receiver to damp the Q of their first and their last resonators. This has a strong effect on their bandwidth and on their passband ripple.

Because you are measuring different bandwidths than the filter specification, I suspect that some of these filters require different source and load impedances to be applied to them.

Passband ripple can have a large effect on how a filter sounds.

David GM4ZNX