{"id":3498,"date":"2016-12-06T22:19:21","date_gmt":"2016-12-06T22:19:21","guid":{"rendered":"http:\/\/lefars.org.uk\/WPblog\/?p=3498"},"modified":"2016-12-07T00:28:52","modified_gmt":"2016-12-07T00:28:52","slug":"tests-on-4-metres-on-the-clansman-353","status":"publish","type":"post","link":"https:\/\/lefars.org.uk\/WPblog\/tests-on-4-metres-on-the-clansman-353\/","title":{"rendered":"Tests on 4 metres on the Clansman 353"},"content":{"rendered":"

John, G8DZH, has converted my email to a few LEFARS members interested in 4 metre operations\u00a0\u00a0into this blog post as hopefully of interest to a wider audience. \u00a0I’d been experimenting with the various settings for bandwidth with different handsets on\u00a0a recently acquired Clansman RT-353.<\/a> My thanks in particular to Dick G4DDP and Selim M0XTA for their assistance, patience and forbearance!<\/p>\n

Manufactured by Marconi Space and Defence Systems in the late 1970’s the Clansman RT-353 entered service in 1979 as\u00a0just one part of the\u00a0Clansman\u00a0suite of equipment\u00a0in the midst of the Cold War and was the most advanced VHF \/ FM transceiver of its day. Designed to be\u00a0immune to\u00a0dust and water ( it was submersible to 1.5 metres) and the occasional dose of EMP (there are valves inside!)\u00a0it offered VHF \u00a0FM \u00a0(voice and data) facilities\u00a0for use in soft skinned and armoured vehicles. Output power was switchable\u00a0from 100mW to 50W in four steps. After receiving\u00a0colourful comments from Dick and Selim around audio quality, I decided to investigate the waveform and bandwidth in standard trim using my newly acquired\u00a0SDRplay<\/a> \u00a0SDR \u00a0monitor receiver\u00a0taking\u00a0screen captures for evidence.\u00a0For comparison purposes I drafted in the trusty Yaesu FT-857D in\u00a0NBFM and WBFM modes on 2 metres.<\/p>\n

The Clansman 353 supports three voice modes :-<\/p>\n

    \n
  1. NBFM \u2013 Clansman 353<\/strong> \u2013 shown here\u00a0modulated just by the 150c\/s subtone \u2013 bandwidth around 5Kc\/s \u2013\u00a0[ignore the spike at 70.469MHz being the LO]<\/em>
    \n    \"trace1\"<\/a><\/li>\n
  2. WIDE FM with 150c\/s sub-audible tone \u2013 Clansman 353<\/strong> \u2013 again clearly heavily modulated \u2013 bandwidth around 8-10Kc\/s just for subtone.\"trace2\"<\/a><\/li>\n
  3. \u00a0WIDE FM no tone \u2013 Clansman 353<\/strong> – much cleaner \u2013 the waveform would have been cleaner but was keying the handset which picked up some low level ambient noise.\"trace3\"<\/a><\/li>\n<\/ol>\n

    Given G4DDP’s scathing commentary of the audio quality\u00a0but not others I suspect the effect of the sub-tone is radio specific creating IM audio products if the radio is susceptible. Bandwidth settings were crucial too to get good audio but on the SDR when set to NBFM with a 12Kc\/s passband the audio quality was good \u2026ignoring the subtone.<\/p>\n

    I then looked at the bandwidth of the signal when modulated by constantly blowing on the Mic in an attempt to create something akin to pink noise.<\/p>\n

    Modulated NBFM \u2013 Clansman 353<\/strong> \u2013\u00a0that\u2019s not very narrow! – 25kc\/s
    \n    \"trace4\"<\/a><\/p>\n

    Modulated NBFM \u2013 Yaesu 857D<\/strong> \u2013 by way of comparison here\u2019s what the Yaesu looks like \u2013 that\u2019s more like it!\"trace5\"<\/a><\/p>\n

    Modulated WBFM \u2013 Clansman 353<\/strong> \u2013\u00a0that is very W..I..D..E – 50k\/cs
    \n    \"trace6\"<\/a><\/p>\n

    Modulated WBFM \u2013 Yaesu 857<\/strong> \u2013 textbook!
    \n    \"trace7\"<\/a><\/p>\n

    And finally a pic of the beast itself cleaned via removal of a thick layer of Iraqi dust.
    \n    \"rt-353-radio\"<\/a><\/p>\n

    Given the strength of Dick’s (G4DDP) objections to the audio, I decided\u00a0the subtone had to go if I was to use the 353 on the Amateur bands. Information around how to do so was found within this\u00a0article\u00a0:<\/p>\n

    http:\/\/5820-99-114.com\/TCRU\/?p=609<\/a><\/p>\n

    It was very simple to do and very effective – a simple tweak of a 10-turn pot whilst monitoring the tx but only after\u00a0spending\u00a0a good 15 minutes admiring the superb quality of the electromechanical engineering. I’ll post some pics of the internals to this article next time I open the box.<\/p>\n

    Once done Dick was heard to say the mod “wasn’t bad at all” on the following day’s QSO, praise indeed!\u00a0Selim described it as very good too. Job done. Will be put to good use on the local 4 metre nets and with 50watts available should be very effective.<\/p>\n

    For those who’d like to learn more about the Clansman 353\u00a0here’s a link to an excellent PDF from Marconi.<\/p>\n

    www.ferret-fv701.co.uk\/radio\/clansman<\/b>_vrc353<\/b>_description<\/b>.pdf<\/a><\/p>\n

    There’s plenty of information available on the net about this and other Clansman radios. At the time of writing (Dec 2016)\u00a0there are still plenty\u00a0of 353’s\u00a0available to buy on the surplus market and auction websites. Prices for a working 353 start around the \u00a3100 mark but can be as much as \u00a3500. I hesitate to think how many thousands they must have cost the taxpayer in 1979.<\/p>\n

    They served\u00a0the British Army well from 1979 to 2010.<\/p>\n

    73s<\/p>\n

    Dave M0IDF
    \nEmail:     m0idf@lefars.org.uk<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    John, G8DZH, has converted my email to a few LEFARS members interested in 4 metre operations\u00a0\u00a0into this blog post as hopefully of interest to a wider audience. \u00a0I’d been experimenting with the various settings for bandwidth with different handsets on\u00a0a … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":27,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"gallery","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[65,6],"tags":[],"class_list":["post-3498","post","type-post","status-publish","format-gallery","hentry","category-operating-reports","category-reviews","post_format-post-format-gallery"],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p22sia-Uq","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/posts\/3498","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/users\/27"}],"replies":[{"embeddable":true,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/comments?post=3498"}],"version-history":[{"count":8,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/posts\/3498\/revisions"}],"predecessor-version":[{"id":3514,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/posts\/3498\/revisions\/3514"}],"wp:attachment":[{"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/media?parent=3498"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/categories?post=3498"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/tags?post=3498"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}