Brandon's Kenwood Basic T2 Component AM/FM Tuner Review

 

I purchased this radio for one reason and one reason only - the AM bandwidth IF slider.  I have never before seen this type of switch on any AM radio.  I purchased this as a combo auction along with a Kenwood Basic C2 pre-amplifier.  The total cost was $164, but the C2 pre-amp sells anywhere between $100 and $150, so I got a great deal on the radio.  I had planned on re-selling the pre-amp, but I like the processing that it does to the audio signal so much that I think I'm going to keep it too.

The slider switch is a smooth slider - there are no "notches" in it.  I was initially suspicious that this may be nothing more than a treble control with bandwidth set at a constant 10khz, but a few quick tests by feeding the audio into my computer confirm that it is indeed a true bandwidth selector.

Based on a graph of an audio sample at both the widest and narrowest settings, the bandwidth specs seem to be as follows:  At the widest setting, full bandwidth up to 9khz and then it rolls off from there.  At the narrowest setting, full bandwidth up to 3khz, then there is a very gradual rolloff to about 8.5khz.  That makes this only a moderately selective radio in narrow, it would be nice if the rolloff was sharper that this.  Minus that one issue, the selector works great in all situations except where the narrowest of selectivity is needed, and with the variable bandwidth, you can find that sweet spot that just nullifies any adjacent interference without sacrificing any more audio fidelity than is necessary.  Reception itself is solid, though unfortunately images of my local 1kw station 1 mile away popped up in a few other places on the dial.  But in my case, I only have 1 local station so this is not a big deal for me.  My other complaint on AM would be that it only offers digital tuning with 10khz steps - you cannot fine tune 1khz above or below.

The FM side is a pleasant surprise as well - upon taking the unit apart, I discovered that there are actually 4 ceramic bandwidth filters - this alone puts this radio in the league of the more expensive $100+ component fm tuners.  My particular unit sounds like it needs a front-end alignment (to be expected I guess for a unit almost 30 years old) so its hard for me to review the FM performance, but in theory, a well aligned unit should be a solid performer on FM (I recently modified a Kenwood KT-880D for a friend of mine - this radio only had 3 filters and needed no alignment and performed incredibly well).  What I can say is that the sound quality on strong local stations is excellent with rather wide stereo separation.  My only complaint on the FM side would be that your only choices are stereo w/auto mute and mono.  In stereo mode, once the stereo signal is lost, the unit automatically mutes the audio instead of defaulting to mono which can be annoying.

Conclusion - a unique, solid performer.  The 4 ceramic filters on the fm side alone would make a comparable unit go for $100 or more.  Add to that the ability to listen to the highest fidelity possible on AM with a unique variable IF slider, and you have yourself $60 well spent.  This is a rare unit that flies "under the radar" so if you can find one ebay, get it!  As of the time of this review, there is actually one listed on ebay - search for Kenwood T2.

Comments

[Angelo]

Very cool.
Nice pick-up.

[Paul]

This must be audio bandwidth, not IF bandwidth.

[brandon]

Yeah, the graph is of audio bandwidth. But the IF slider itself does indeed change IF bandwidth, not audio bandwidth. I confirmed this in a separate test by recording an audio sample 10khz in frequency away from my local AM station (1480 is the local, I set the dial to 1490) and applying a 3khz low pass audio filter with gradual cutoff to the wide audio sample and comparing that to a sample recorded with the IF bandwidth set all the way to narrow - the results were totally different, confirming that the slider isn't just the equivalent of a treble control.

[Paul]

I am pretty sure the IF bandwidth is not continuously tunable. This is a feature which we've just not begun to have in software defined receivers. At best there are multiple IF bandwidths, maybe two or three, and the slider switches between them. Even then, such a selectable IF system must have made this tuner very expensive back when it was introduced (what year is this tuner from?).

One other possibility is that the radio employes IF shift, such as the system in use in the Eton E10. I think this is liklier.

[Paul]

oops, I meant "is a feature which we've just begun to have", without the "not". Sorry.

[brandon]

If Jeff is able to upload an .mp3 file to his server, I can post one on here. Maybe you could tell by listening to an audio clip exactly what the slider is doing. In the clip I'll slowly move the slider from wide to narrow on an adjacent channel - this will work better tonight when I have signals on adjacent channels. The T1 was produced in 1982, this was the follow up to that receiver, so probably 1983-1985ish

[Paul]

Among the best receivers we had circa 1986 was the JRC NRD-525 with two built-in filters (4 and 2 kHz), and two more slots for additional filters you could purchase. It sold for around $1,000. No continuously tunable IF filter. See

http://www.universal-radio.com/catalog/commrxvr/nrd525.html

and
http://www.dxing.com/rx/nrd515.htm

[jeffrey McMahon]

I'll try to upload the MP3 file, but I've never done it on my typepad blog before.

[Paul]

Sony ICF-5900 for $15 - SF bay area:

http://sfbay.craigslist.org/pen/ele/1636895817.html

[brandon]

I found a free mp3 server to upload it to.

So anyways, the audio clip is as follows:

In the first 16 seconds, I start with full bandwidth and apply a filter (via computer software) that is the equivalent of turning the treble down and then back up (variable bandpass from 10khz to 3khz then back up)

Then from 0:16 to 0:30 I turn the IF slider down and then back up.

Then from 0:30 to 0:35 and 0:35 to 0:40 I do a direct comparison of audio filter vs IF filter. I think the difference is enough to show that the slider is doing more than just audio filtering because the IF filter definitely removes more adjacent interference than the equivalent audio filter does. The remainder of the clip is just a sample of a local station at full bandwidth to show the high fidelity of this receiver.

http://kiwi6.com/file?id=og0a6bk8u6

[Paul]

Very interesting. Yes, there is something more than just audio filtering going on here.

Here is the little I could find on the Kenwood Basic T2. The AM section is apparently extremely good:

http://www.fmtunerinfo.com/kenwood.html

Kenwood Basic T2: Unlisted in the Orion Bluebook, the quartz-synthesized Basic T2 is a mystery to us, except that it's clearly a far better tuner than the Basic T1. We've just learned that it has Wide and Narrow IF bandwidth settings for FM, as well as an unusual adjustable slider control for variable IF bandwidth on the AM band. It uses Kenwood's "DLLD" (Direct Linear Loop Detector) technology, their name for a PLL detector, that can also be found in the KT-3300D and KT-5020, among others. Our panelist Bob says, "The Basic T2 came after the KT-9XG, which has a very similar, if not exact same, signal meter display. The T2 appears to be the first Kenwood tuner to use the DLLD. This was a big change point for Kenwood, as the KT-9XG still had the Pulse Count Detector." Our contributor Keith lauds the T2's "excellent AM section, very immune to interference/static." The T2 turns up on eBay occasionally and usually sells for $20-65, with a wacky high of $129 in 6/07.

[Alain]

If you can read the schematic you will see that AM variable IF BW potentiometer in fact allows a selection between normal audio detector output pin13 of the LA1245, and Smeter output pin16 used as an AM detector with a narrow ceramic filter CF6 in its IF path : it is a real clever IF bandwidth selector. Alain

[Alain]

In addition : this tuner contains 4 FM ceramic filters, but in FM wide mode only 2 are used , plus 2 IF transformers. In FM narrow mode the 4 filters are used: 2 wide and 2 narrow BW, plus one IF transformer. I could not find the datasheets of these filters. Are they constant group delay ? Alain