  We present new images and continuum spectral analysis for 14 resolved
Galactic SNRs selected from the 74 MHz Very Large Array Low-Frequency Sky
Survey Redux (VLSSr). We combine new integrated measurements from the VLSSr
with flux densities extracted from the GLEAM and measurements from the
literature to generate improved continuum spectra. We combine the VLSSr images
with publicly available images at 1.4 GHz, to analyse the resolved morphology
and spectral index distribution across each SNR. Three of the SNRs, Kepler,
G28.6-0.1, and Tycho, have integrated spectra which can be adequately fit with
simple power laws. The resolved spectral index map for Tycho confirms internal
absorption which was previously detected by the LOFAR, but it is insufficient
to affect the fit to the integrated spectrum. For the pulsar wind nebulae
G21.5-0.9 and 3C58 we identify high-frequency spectral breaks at 38 and 12 GHz,
respectively. A low frequency spectral turnover adequately fits the data of the
remaining nine SNRs. For Kes 67, Kes 69, Kes75, and 3C397, we attribute the
absorption to ionised gas along the line of sight, possibly from extended HII
region envelopes. For W41 the absorption can be attributed to HII regions
located in its immediate proximity. Thermal absorption from interactions at the
ionised interface between SNR forward shocks and the surrounding medium were
previously identified as responsible for the low frequency turnover in SNR
3C391; our integrated spectrum is consistent with the previous results. We
present evidence for the same phenomenon in three additional SNRs, Kes73, W49B,
and 3C396, and derive constraints on the physical properties of the
interaction. This result indicates that interactions between SNRs and their
environs should be readily detectable through thermal absorption by future low
frequency observations of SNRs with improved sensitivity and resolution.
